You pay a bunch of money to someone who has a Dash 8 or similar common commercial aircraft. These drones probably don't have 1000mi range.
And even if you can't follow one all the way to its destination you can still take some real good pictures with flash and plaster them all over the news and wait for someone to say "I pump fuel and sweep floors at airport X and a bunch of dickbags with black suburbans and bad attitudes have a hanger full of those things".
Since you're replying to a question about tracking fixed wing it's worth mentioning that their range can be well over 1000 miles as some of the Iranian Shahed drones have a range of almost 1600 miles.
That's a 400 lbs, 11 ft by 8 ft UAV powered by a 50 hp gasoline piston engine. It's half the size of a Cessna 172 and makes a similar noise, observers would for sure classify it as an airplane.
A Dash 8 or other similar commercial aircraft lacks the radar necessary to track an aerial target. Most airliners have weather radar but it's not really useful for this purpose. In much of the airspace around that region a Dash 8 would also have to operate under ATC control; the pilot can't just fly wherever without getting violated.
Yeah, unless someone really really big is behind this (or it's aliens), then a US military drone should be able to track and follow one of the unknown drones for a while.
Nah. None of the publicly acknowledged US military drones carries the type of X-band air search radar that would be necessary to reliably track a small aerial target. There is some stuff in development with that capability but it hasn't been fielded yet, and for safety reasons it certainly wouldn't be authorized for flight in controlled civilian airspace or over populated areas.
How exactly do you follow a fixed-wing drone? Some of the high-end/industrial drones has pretty impressive ranges.