Is the night bus safe in London?

At around 4-5 am. I have to go to the airport and taxi is too expensive

You're a female, right? Typical! Women are such weak, helpless cowards! When are you gonna grow up and stop being such a girl?

Stay downstairs just to make sure and keep your luggage where you can see it.

It isn't too bad; just make sure you sit downstairs as close to the driver as you can, don't leave your bags in the luggage rack unless you're sitting right next to it.

Be aware that a quite a few homeless people use the night-buses (particularly the airport routes) for somewhere to get a couple of hours sleep in the warm; they don't usually cause any problems if you leave them alone.

Yeah, reasonably safe.

There's nothing much that's completely safe in London these days. Mostly it's fine, but you can encounter aggressive drunken people, those with severe mental illness who may be violent or pests, and those who have robbery or pickpocketing in mind. I'd say go ahead, but sit near the driver and keep your wits about you. Or, go early on a National Express bus and hang out at the airport until it's time for your flight.

I think there's a 24 train.

Yes they are mainly very safe. Just in case sit near the driver and keep your luggage with you

Yes, they are usually very busy. What airport near London is open at 4am?

I've never encountered anything worse than the predictable drunks singing rude songs.

It's usually fine. Occasionally you'll see somebody drunk or mentally ill but they're usually just a bit noisy and no real danger. At that time some of the passengers will be going home from a night out and some will be on their way to work. If the bus is a double-decker just sit downstairs so you have more options to get away from trouble or ask for help.

Some night routes get very crowded, so it's best to board before it reaches the busiest areas, especially with luggage. However, try to select a stop that isn't isolated - a potential attacker is more likely to target you there than on the bus. If you can board at a major bus interchange / station, preferably at the start of the route, then there will be plenty of people around and room on the bus. Another option is to wait somewhere safe nearby, using your phone to track the bus. Then you can approach the stop when the bus is only 1 or 2 minutes away.