First you isolate the telescope from the airplane by mounting it on a spherical pressurized oil bearing. The plane shake and quakes, but the telescope doesn't feel it. Second, you direct the wind away from the telescope by shaping the side of the airplane so as to deflect it, and install a little deflector fence on the edge of the telescope cavity as well. The object would eventually be out of the field of view, even if you could adjust the telescope. A few hours is generally the maximum.
Objects make arcs through the sky due to the Earth's rotation.
The motion of the airplane also adds or subtracts at bit from this apparent object motion. So, while observing a target, the telescope appears to be following an arc in the sky, although it is actually staying fixed dead-on to a distant point in deep space that just appears to me moving. All that time, the airplane body slowly swings in its own arc relative to the ground to keep the target at a right angle to the airplane, so that the telescope can keep peering out. Typically, after a few hours, the object has either set too near the horizon, or risen too near the zenith to track, or else the airplane has been flying so long in one direction, it is getting too far from home. At this point, another object, located in a different part of the sky is turned to.