Slitherine

i just bought this game and im in the german camp. the 3rd scenario i have 3 bombs and 6 targets. they want me to bomb all 6. they tell me i can land at the airport however there is no manual so i dont know how to land. ive flown over the airport and the green marker, down the runway but the plane doesnt land. i tried landing in an earlier camp and the plane crashed. so how do i land in this game? thanks