I’ve always thought my airport only operated regional jets for the mainline carriers at my local XNA. I know Allegiant flies the MD-83 to my local airport but recently I saw a 717-200 from Delta. How could I confirm this?
You could use google and common sense.
For example, any idiot would know not to fly a 747 into LGA. Google can tell you that 767s are the largest regularly allowed airplanes into LGA
If you know the registration, search it on flightaware or other flight tracking websites.
Wikipedia. not always 100% accurate but most have a list of all the aircraft and routes.
FlightRadar and many common travel agents
Just go on Wikipedia and check the Wikipedia english page related to your airport. There is always a section called: " Airlines and destinations ".