Originally Posted by
CaponesCPA
Haven't been to either yet, but am flying into T3 on Aer Lingus but out of T5 on BA Club World. I teased the T3 idea as well but I read you'll have to go through security in T3 to get to the terminal side and then back out and through security again in T5. Sometimes it causes issues having your boarding pass scanned twice and likely isn't worth it unless you have a 5+ hour layover. We have a 2.75 hour layover and will go straight to the T5B BA Lounge.
This is incorrect/outdated.
BA now uses T3 for departures (arriving at T5). Aer Lingus uses T3 for arrivals and departures (thanks to prevlearance).
There is a bus from T3 to T5 that goes post-security, you don't have to go through twice.