You want a captive audience, many with money and valuables in their possession? You want a sky-heist. This is basically aircraft hijacking without being aboard at the time. It's logistically demanding.
Requirements: first, if you cannot fly as fast as an airliner, do not do this. Top speed here is about 900 kph, at an altitude of 9000 meters. This is fast and cold and can be uncomfortable if you are not a fully adapted flier. Test yourself out first.
You will also want a ground team, and one or more large trucks - one person at minimum to drive each truck. You can also use a refurbished school bus if you remove the seats. These are often available cheaply, but you can steal one if you wish.
Planning: You begin by picking a flight. This can be anything, of course, but you should prefer flights to or from your area, and flights on days around major business events. For example, the day before a major industry holds its conference in your town. The airlines will publish their flights days in advance.
You will also need to pick an airport where you will set down. This is where your ground team will meet you. Have them find a good place to park the trucks off the roadway where they will not attract suspicion, until you are ready for them.
Do research on how to properly enter the plane. Try not to enter via the cabin doors. This will unseal the cabin and cause a lot of panic, which is good because you don't want people to immediately respond to your presence. However, the drop in cabin pressure cannot be allowed to remain, so you will need to re-seal the door after boarding. You should prefer using one of the cargo doors.
Execution: Get in position to track your chosen flight's takeoff, then come after it. After about 15 minutes, the plane should have achieved its proper altitude and cruising speed. Your objective will be to board the plane without disrupting its ability to stay aloft. Your goal is theft, not murder. Open the door you chose, like a cargo door, then make your way into the cabin.
Announce yourself and your intention. Inform the cabin crew that they should keep the passengers calm and quiet, and that nobody will be hurt if they comply. At this time, you should also mentally pick out a couple of hostage candidates. Don't take them hostage yet, but just remember where they are and how to get to them. You prefer women and children, but not babies, for the sympathy factor.
At this time, go forward to the cabin. The pilot and copilot will have long since become aware of your presence, and will probably have radioed in to let the authorities know. This is fine, detection is unavoidable. What you can't let them find out is your chosen ground base. To that end, you want to destroy the radio and the transponder - they are normally right next to each other.
Give the crew your new destination, then head back into the cabin. Start confiscating cell phones. Assume that everyone has a cell phone, and demand it from them. Make examples of those who claim not to have one, but don't be violent. Your goal is to prevent passengers from calling the authorities independently for as long as possible.
After a few times of this, I modified my strategy a bit. I would bring along garbage bags or sacks, and demand that passengers throw their wallets or purses into the bags. If the plane were to be intercepted, I personally could still fly away having made something for my trouble.
Once on the ground, your goal is to unload the plane as rapidly as possible. Passengers should form a bucket brigade in the aisle, passing bags from overhead storage and under the seats to the rear of the plane. Have a truck ready to be loaded with these bags. Your other support crew will be loading from the cargo compartment of the plane.
Exit Strategy: This caper can go wrong at several points. In the most ideal case (your trucks leave the scene unmolested), have them take different routes. You can re-converge at a second agreed-upon meeting place to unload.
If the law finds your landing site, simply fly away - your ground crew should try to drive off separately, and hope for the best. If you have powers that can hinder the police pursuit, stay around long enough to do this, then leave.
I've found that passengers start getting uncooperative at the time you land. They start thinking they have a chance, that rescue is a possibility, and that resistance is viable. I found that taking their cell phones early helps to demoralize them on this front. If they feel like there is no hope of contacting the law, they may not be so ready to resist. Nevertheless, make quick and efficient examples of any passengers who don't cooperate.Individual plans will be more detailed than this (but she also calls out the research you need to do), so all in all I think this is a great caper. Thanks, AA, and happy flying!