Some of the drones Ukraine is using are converted prop-planes (same style as Cessna 152) and others are old Soviet Union drones that also look like small planes.
Quadcopters are used in and near the frontlines but they don't have the range to attack far out targets in Russia.
The biggest reason why Russian AA shouldn't be confusing Ukranian long range drones with airliners is that that the airliners are much larger and fly high (at 30,000 feet +) whilst the drones fly much lower exactly to avoid AA.
Ju$tice