IAD made us freak out about first port of entry. It was about 11 years ago, we did CPH-IAD-MCO. Queued at IAD immigration for 3 hours, missed our MCO flight. Rebooked on a later fight after struggling to get our bags and re-check them. We finally boarded the plane and after 30 minutes we all had to deplane due to tornado at IAD and we were told to stay away from the glass windows.
After a long time, the tornado was gone and unfortunately the crew has passed their duty hours so they need to find a crew to get us to MCO.
We were supposed to arrive at 5pm but ended up arrive at 5am and found out that our lock for the luggage was broken and there is a TSA slip in it. My friend told me that TSA cut his duffle bag open and it's not usable anymore.
So our conclusion was: avoid first port of entry where possible, and suitcases with built in TSA lock.