Airplanes Bonuses

[abulbulian]

At one point do your planes start getting a bonus to combat? Which tech breakthroughs do you needs.

Also WHAT amount of bonus does each tech gain. Example how would a plan start getting bonus +1, +2, +3?

Do you need to buy them again to get bonus or do the current planes you have get upgraded automatically?

[Tamas]

At one point do your planes start getting a bonus to combat? Which tech breakthroughs do you needs.

Also WHAT amount of bonus does each tech gain. Example how would a plan start getting bonus +1, +2, +3?

Do you need to buy them again to get bonus or do the current planes you have get upgraded automatically?

They get upgraded automatically IIRC.

And there are lots of techs affecting the airplanes, because you can improve their attributes separately.

[abulbulian]

So what is the starting point (best practice) to upgrading planes? Anybody have some experience at this? From low to high?