Revealing mistake: When the terrorists drop the dead body out the aircraft door, look closely at the aeroplane just beneath the door, you can see the reflection of the mat the stuntman lands on, as well as the spotters around it.
Revealing mistake: When Rane jumps out of the hospital window and crashes through the umbrella, table, and people, you can see him land on an air mattress. Even though it's camouflaged to match the ground, you see it deflate under his weight.
Answer: It's been a while since I've watched this movie, but he obviously knows the plane is hijacked. It's a pretty safe assumption that the agents are dead as they're escorting a dangerous, high profile prisoner. Pretty easy to connect the dots. Alternatively, they could've failed to check in, and he assumed the worst.