BA require each BA001 service to have a service aircraft and a serviceable standby.
When the relaunch started, we had 3 operational aircraft. So one for the BA001, one standby, and one being serviced, usually the one which did a BA001, then turned around for the BA002 the previous day, but all 3 were often operational.
When the 4th aircraft returned to service, we could overnight at JFK allowing the BA002 to return to it's usual morning JFK departure.
But as periods of significant maintenace downtimes approached, (OAG is scheduled for a big Inter 3 check in about 80 flying hours), you would need the 5th aircraft to maintain this service.
OAC is the 5th aircraft and OAC's mods are complete, but the big problem with operating such a such, specialised fleet hit yet again.
When each aircraft starts flying, it's 'clock' counting down to scheduled maintenance started ticking again.
OAC was found to require a new lower rudder late into the input, the next available one was scheduled for delivery in late July, OAD also needed one as it's lower rudder would be time-ex on 13th June, and that aircraft is now in for a week-long scheduled service check now, the rudder is expected on the 15th June.
(AF had no spares, and where else can you go to with no other operators?)
So BA had a choice, maintain services as they are and risk possible cancellations when the usual maint problems possibly combined with one or two aircraft also in scheduled maintenance, or do a temporary retiming of the BA002.
(So far this year we've only had to use the 001 standby aircraft twice, but robustness of service is the top priority).
As loads dip somewhat between late June-August, if a retiming had to be done, now's the time, though no one is pretending it's an ideal situation, customers were informed well in advance.
The operational aircraft have been worked hard since November, there is another Service check input on OAE right after OAD completes.
So the return of the BA002 to it's normal slot so early in the relaunch was a calculated gamble, and this time it did not go our way.
Expect the BA002 to return to the 08:30 JFK departure by early/mid August.