I've found the best way to get a jet is to go in via Merryweather Helicopter.
1. Call Merryweather For Helicopter Pick Up
2. Get In Chopper (DO NOT KILL PILOT)
3. Open up your map and mark a waypoint in second box (on the right) next to the runway.
4. Tell pilot to go and soon as you get overhead hit O or B
5. Repel down if the option is there if not jump but pull your chute right away and land right next to the cockpit
6. Get in take off right away don't drive to the runway.
7. Soon as you're in the air do a 180 and fly south make sure you fly stright up into the air the rockets WILL ALWAYS miss
8. Enjoy your jet
9. Repeate as needed
I've never lost or failed to get a jet while doing this