If you reside in a historic district, to conduct work to the exterior of your historic property, you are required to obtain a Certificate of Appropriateness (COA). A COA is a special permit obtained in addition to the regular building permitting process.
The recommended arrival time at the airport is 75 minutes prior to departure when traveling within the United States. You must be checked in at least 30 minutes before your scheduled departure time.
May 08, 2009, 5:37 PM. I agree with the suggestions to arrive at Heathrow about three hours before your flight. As other posters have noted, the length of time required to check in and clear security varies wildly. I've been through in as little as 30 minutes, and as long as 80 (particularly bad day!).