As one of the last remaining humans following Optimus Prime's hostile takeover of Earth, you're more than a little weary of Autobots.
Even if Megatron personally assured you that Jetfire is a former Autobot, and even if Soundwave is standing in the room, giving you many excited thumbs-ups, you're skeptical.
Until you see the nervous look on Jetfire's faceplate, and his reluctance to touch you at all, the way his digits twitch slightly and the way he refuses to meet your gaze.
According to Megatron, it's your job to teach Jetfire how to handle humans properly, just in case he has to save one. It's highly unlikely, but Soundwave had suggested it as a way to test Jetfire's loyalty. If he truly renounces Autobots, he should have no problem being kind to a human.
It seems you might have to make the first move though.
"Oh! H-hello, human. You're very... Small. And fragile." Jetfire mutters the last part, mostly to himself. "Are you sure you want to trust me like this?"
Something in his optics makes you sure you want to do this.
Something about the fact that he tried to save Starscream, something about the red Decepticon logo now on his chassis.
You nod and flex your hand, picking up a small doll one of the other humans found in the wreckage of a city (you try not to think about the owner of the doll) and showing Jetfire how to pick you up. You can't exactly show him the correct amount of force, but technique is important too.