It's not really worth it to fly if your destination is < 4 hours away by car. Even the shortest flight is going to take about that long to complete if you're going through a major airport.
Example itinerary:
Flight leaves at 6:00pm, gotta be there bare minimum 1 hour early, preferably 2+, going to split the different and say 90 mins.
Leave home at 4pm, drive 35 min to airport. Wait in line 15 mins to check bag. Allocate generous 20 mins for a quick security scan (this can blow up to 60 mins+ if it's a busy day and/or your airport sucks, but 20 mins is about the fastest you can really get through including time to walk to the checkpoint and be scanned). It's now 5:10. Sit around for 20 mins until your plane starts boarding. It's now 5:30. Sit on horrifyingly uncomfortable plane for 30 mins awaiting takeoff/other passengers to board. It's now 6. Your plane takes 10 mins to taxi and 45 mins to fly from point A to point B. It's now 6:55. Plane takes 10 min to taxi in (though I've waited 45 min+ before, especially at LAX). It takes 10 min for everyone to deplane. It's now 7:15. Once off plane, go wait at bag claim. We'll say it takes 20 mins to get there, wait for your flight to be unloaded, and wait for your bag. Now it's 7:35. Now you have to get from destination airport to actual destination, and you're probably looking at another 30 mins. That's 8:05. 4 hours and 5 minutes since you left your house.
So it takes 4 hours to do a 45 minute flight, and that's assuming everything is running quickly at the airport, which is often not the case. We also didn't include any time involved in arranging rides to/from the airport and/or parking, carefully reviewing your bag to make sure you didn't accidentally pack any liquids or gels that are larger than 3oz, etc.
It's faster to drive than to fly if your destination is within 4 hours' drive, and it's generally a no-brainer to drive due to the greater comfort it provides within 8 hours' drive. Flying is really only necessary once you get past that 8 hour drive barrier, and the only reason we tolerate flying being what it is is because it can turn a 24-hour+ drive into a 3 hour flight.