- Switch 25mm cannons to 7.62, they are more accurate and can damage jet more.
- Move! Don't let Jet line up with you. Change altitude and direction when you see attacking jet. Use terrain to hide from Jet.
- Use you base automated AA-turret. Spotted aircraft automaticaly targetter by it. If you can't deal with Jet yourself, retreat to base.
- Igla launcher will give engineer more range than Stinger: 450m vs 350m.
Since you have SOFLAM, you also can try to use Laser-Guided Helicopter missiles. They can be launched on laser-designated jet. Try it.
Equip pilot as Support with Ammo squad upgrades. With 4 level squad perk it will resupply onboard engineers with rockets.