Pull a fire alarm. Sneak through security or run past the TSA agent falling asleep near the exit of the secured area. Try to open one of those secured doors marked "alarm will sound". There's lots of ways.

Note: This is not actual advice. Not responsible for any resulting fines or prison sentences.

Very annoying but not super bad.

1. Buy tickets to a bunch of flights on any day.

2. Check-in luggage with a raspberry pi inside with a bunch of electronics coming out of it and two powered 8 segment displays.

3. Do not board any of those planes.

All those planes will be delayed while they remove your checked luggage from the hold since nowadays planes don't take-off with luggage if the traveller doesn't also board. With all planes delayed you can probably choke the runways and delay all departures.

Using F#

(edit: This made sense before someone uncensored the title)

Scatter lots of birdseed around them. Probably not even illegal.