I was on the JFK-MAN AA210 19/5 and we were delayed 3.5 hours landing into Manchester due to 'electronics overheating'. We got all the way to the takeoff lineup at JFK before the captain came on and said we had to turn around and go back to stand.
Get back to stand, told the problem would take 3 hours to fix or they had a spare plane they could turn around in 2 hours. Anyway, ended up taking off around 23:30, four hours late. Credit to AA, they did bring food and drinks (quite a lot of it too!) to us at the gate but I looked on FR24 and the plane had not flown since the night before so you'd think they may have spotted the issue before our flight.
The real annoyance I had was not the flight delay but the delay in getting bags once we landed. Landed at 10:30, first bags came out at around 11:45 and I didn't leave MAN until 12:10. I noticed the PHL flight was delayed also and landed just before ours so assumed this could be why there was the delay. Definitely didn't seem like a good day for AA at MAN
Slightly annoying that EU261 isn't due as it wasn't an EU carrier but these things happen!
As a side note, the flight was nowhere near 100% full in economy, I had two seats to myself and I know many others did. Business seemed fairly full however.