How early are passengers allowed to enter into an Airport?

This question is often faced by many budget travelers. How early are we allowed to enter the airport? If I have 6AM flight can I enter at midnight and sleep for 4 hours before being allowed to check-in? Answer to this question is very complex and depends on dozens of parameters. In this post, I have made an attempt to simplify and explain the same.

We often book cheapest available flight for our intended departure dates. Cheapest flights are usually ones departing very early morning or late night, often called red-eye flights. They are usually cheap because most corporate travelers, those who prefer some comfort and convenience avoid these flights as they don't want to spoil their sleep middle of the night to drag themselves to airport. They would rather chose a more comfortable flight timing little later in the day, even if it is expensive.

But in situations where one has an early morning flights- either because it is cheap or it is the only flight available (most international departures often happen early morning), next question arises- where to spend the previous night? For those arriving from other cities and even for those who stay in same city but don't want to spend huge sum on early morning airport taxi, most tempting option is to reach airport late evening and try to sleep over inside for a few hours.

Reasons for trying to sleep at airport are many.
1. Hotels near airports are often very expensive- probably more expensive than your flight itself. For budget conscious travelers makes no sense to spend so much for just a few hours.
2. Staying in city and reaching airport early morning is an option- but if city's public transport doesn't operate during midnight-5 AM time, then passenger has to spend lots of money on airport taxi- again may not make economical sense.
3. Trying to reach airport just in time from your home city/origin is an option- but this carries a risk of missing the main flight if train/bus/flight gets delayed for whatever reason. So to have some buffer for possible delays those arriving from other cities need to arrive much early.

Is it legal to reach airport early and sleep?
There is no Yes or No answer for this. Reason being, airports are designed to move people- Passengers are expected to arrive, check-in, proceed to security/gate and fly out. Airports are not designed to provide sleeping places for those who come in early. That being said, most airports DO NOT have an official policy as to how early a passenger can arrive. This largely depends on following factors:

Even the best of airports in the world- like Changi Singapore- that have amazing facilities inside- can be accessed only after you clear security. Changi has sleeping lounges, movie theatres, several gardens, hotels, swimming pool and so on. But none of these can be accessed if you arrive too early for your flight. Facilities are minimum for visitors who have not yet cleared security and customs. (You can see Kinetic Rain though)

Factor 1: Airport operating hours
While most large airports operate 24x7, many airports in smaller cities shut down for the night. This could mean airport premises will be locked after passengers from last flight have left and will be opened only in time for passengers of first flight of next day. For example, airport in Port Blair, Andaman opens only at 6 AM for the first flight of the day at 8 AM. Even if you reach at 5.45 AM you will have to wait till 6/6.10 AM for airport gates to open. In such airports there's no possibility of entering early.

Factor 2: Security check/airport entry process:
Airports in India are manned by CRPF personnel- they check ticket of every passenger and let them in only once satisfied. Thus if you're trying to enter way ahead of time, you are very likely to be denied entry. Like I said earlier, there's no fixed rule on how early one can enter- you might be able to convince the officer to let you in, if you have a valid reason. Again, security officers need to factor the crowd- they don't want too many people inside the airport premises- this will be a security concern and also inconvenience to other passengers who are on time for their flight. Thus if airport is small or security threat perception is high or if crowd is too much, you are most likely to be asked to come back later. If you are lucky, you might be allowed in. If you're trying this route, be polite, have a strong reasoning why you can't come back later and a plan B if turned back.

Airlines typically open check-in before 3 hours for international, 2 hours for domestic. During high security/peak traffic days you might be advised to come an additional hour early. So as long as you're within 3-4 hours before departure time you should be allowed to enter- much earlier than that-often at the discretion of CRPF official. If they are strict you may have to come back later.

Airports in many western countries do not have any checks at main entrance- anyone is free to enter. In such cases you can easily enter the airport, find a corner and be able to sleep for sometime. But again, every area of an airport is monitored on CCTV and if security staff feel concerned, they might arrive and check your ID, ask you to leave or take any measure as deemed necessary. Airports abroad are often spacious, less crowded and a few people sleeping in a corner is often overlooked as 'Not a problem'- but you never know.

No one likes being inconvenienced by sleeping passengers- if where you are sleeping is causing inconvenience to other passengers someone is bound to complain or officials will be forced to take action. This can happen if airport is smaller and sleeping passengers are blocking access to toilets, or self check-in kiosks or other facilities in the airport.

Factor 3: Level of automation.
In some airports you can self-tag and drop the bag, or enter security area with mobile boarding pass. In such cases if the system lets you through several hours ahead of your flight, you can get to the other side of security and enjoy all facilities available for passengers waiting to board the plane.

But if you need to visit the counter for bag drop/document check etc then you will have to wait till they open.

Why can't airport hotels provide rooms at hourly rate?
This is a good question- Instead of charging say INR 2400 per day per room, why can't hotels offer rooms at Rs 100 per hour? This looks like a fair ask but has many complications

1. Each room has a fixed cost- cost of providing clean towel, bed sheet, consumables etc. If this has to be repeated every hour, then housekeeping cost and effort will be too much.
2. If offered at hourly rate, even those who would have paid full day price will opt for hourly rate, which might lead to loss of potential revenue.
3. Most luxury hotels don't want crowd. They only need richer customers who can afford to spend. Allowing huge crowd looking for cheap place to stay will spoil the experience for premium customers

Your alternate options if you can't enter airport early:
Option 1: Hostels/Cheap hotels nearby: However, if you can carefully scan websites like booking.com, airbnb, you might be able to find a place to stay within reasonable rate not too far from airport. I have been to hostels within a few kms of airports in various cities, charging just around 1000 INR for a day.
Option 2: Wait outside airport entry gate: Most airports in India will have some space/seating for visitors outside the departure hall entrance. If you are not allowed inside, you will be able to sit here- but you'll be subjected to winds, no access to toilet and constant sound of vehicles and public.
Option 3: Visitor ticket: Many airports sell a visitor ticket, which gets entry into certain portion of airport, meant for family members to see off passengers. If this access space is good enough for you you can try enter and stay for a while.
Option 4: Try a train/bus ride: If there's a metro/train/bus operating from airport to day a destination an hour away, you can spend 2 hours sleeping on it reaching that destination and then coming back. Good option if ticket fare is not too expensive and if you don't have lots of luggage to take care of.
Option 5: Book connecting flight: Transit passengers will get access to transit area and can spend lots of time there. For example, if you're flying to Europe from BLR but you're coming to BLR from nearby town- say Mysuru or Madikeri etc. If you book your flight like MYS-BLR-LHR or IXE (Mangaluru)-BLR-FRA such that Mysuru/Mangaluru to BLR flight arrives late evening then you will be given access to transit area soon after arrival where you can sleep overnight. Transit passengers can't be forced to go out of airport and come back later.
Option 6: Arrive just in time- if there's convenient transport available to airport just in time for your flight, might be good idea to take it than trying to sleepover.
Option 7: Book a flight later in the day. If for a few dollars more if there's a flight a few hours later in the day, it might be worth the money compared to all the trouble of trying to figure out where to sleep the night or spending lots of money to reach airport/on hotels nearby etc.
Option 8: Airport dorms- Some airports do have facility for passengers-like this one below- not sure how to access it from outside as I saw it in transit area, but no harm checking

Related: Goa minister slamming tourists sleeping in airports- Read this news . No one likes people sleeping in airports- it is a loss for tourism industry if you are not spending money on hotels, taxi etc and sleeping free in airport. Most of our railway stations are always crowded at night with people sleeping all over in haphazard manner- certainly we don't want that at airports. But air travelers are also price sensitive and are often forced to make compromising decision for lack of budget alternative or value for money aspect. Somewhere we got to draw a balance.

What about day time?
Like your flight is at 6 PM but you're arriving in city by 6 AM- what to do?
During day time you will have lots of options- find a place to keep your bag- most railway stations have cloak rooms- spend time visiting some place of tourist attraction, visit a mall, watch a movie etc and go to airport in time for your flight.

What about arriving passengers?
Like you're landing at 2 AM- Is it OK to stay till 6 AM?
Again airports have minimum infrastructure for arriving passengers, as they are expected to collect their bags and leave. No official rule on max time one can spend after arrival.  However you might be able to wait in baggage collection area for a few hours. If airport is closing or if you fall asleep after everyone has left, you are very likely to be questioned by security and asked to leave.

In many western countries arriving passengers get mixed with departing passengers- so unless you've checked bag, you can spend more time in gate area before leaving the airport.

My experience:
Abroad: In every airport I've gone for early morning flight I have seen at least a few backpackers sleeping around. But their number is very few and are often ignored by security staff, though at times they might be asked to move to a different place due to reasons like cleaning, inconvenience to other passengers etc. If security forces feel you're not a genuine passenger you might be subjected to inquiry. Reaching airport abroad costs lots of money in travel/bus/train fare/parking etc so people won't go to airport unless they've a reason. Since airports are spacious and crowd is less, few sleeping passengers are often ignored.

In India: Some large airports like Delhi security may take pity and let you in a bit earlier but in most airports arrive too early and you carry a big risk of being turned away and asked to come back later. 4 hours before international, 3 hours before domestic is the max they would usually allow.

Special scenario for VVIPs
If you are VIP then rules are different- you can access VIP Lounge in airports and spend as much time as you please. But then, if you are a VIP you most certainly don't want to spend time in airport as you will have access to better facilities and more important work to do.