What? You’re flying out of DCA and coming back? Why wouldn’t you just leave it at home.

Saw you said you’re from philly so I’ll mention something that you may not have noticed, DCA is in Virginia and you wouldn’t necessarily have to travel through DC to reach DCA. Virginia gun laws are what you need to be aware of

Do you have a gun safe in the car? If not, don’t leave it there.

You’re not taking it home with you? It’s been decades since I've been to an indoor range, but don’t some of them have places you can store your guns? Maybe rent a locker/safe at one of these places til you get back.

Why would you not just leave the firearm at your home? It doesn't seem safe or smart to bring it in your car to DC just to leave it in a parking garage, and it's very easy to get in trouble while trying to fly with one.

If you must leave it in your car for some reason, buy a gun safe and secure it in a locked trunk. If you drive some sort of hatchback or SUV where you can't conceal it in a trunk, don't do it. The last thing you need is for that gun to get stolen from your car and used in a crime.

I've never had any issue flying with one in checked-in luggage from any of the local airports -IAD, DCA, and BWI. Use a hard case, take ammunition out of gun, and use a lock. Ammunition can be inside the same hard case with the gun and magazine; however, the gun must be unloaded. Tell the agent at the ticket counter and they will instruct you on what to do. Some ticket agents are inexperienced, yet they should call someone with experience in such matters.

By the way, do not fly into or through any of the NYC airports with a checked-in gun. They do not honor the federal laws on flying with guns.

You were intending to leave a firearm in an unattended vehicle at an airport parking lot? Do you have a PA LTCF? How did you intend to traverse MD, DC, and or VA with the firearm? Do you have license and or permits in each state you would traverse? If not, would you have the ammunition and weapon separated?