Yes, it shouldn't happen (e.g. by putting the stansponder in standby before setting the code) but it's not as though it would trigger a real emergency response by the ATC just because it's got cycled through 7700 - it should be reasonably clear a moment or two later that's what happened. While it shouldn't happen, it's in a way a non-issue issue that only alarms people watching flights closely on the likes of Flight Radar because the data capture is not fully live. If the ATC got alarmed, it'd have been momentary too.

For all I know, they might well have had a reason to squawk 7700 on this particular flight which was subsequently resolved, though.

It's my understanding that ATC can sometimes ask a flight to sqwuak 7700 as it then highlights that flight on the controller's radar screen. In the situation described in this thread, I could see this happening as it would allow the controller to instantly see the aircraft on his screen and be able to deconflict it from other traffic.

Just thinking about last yesterdays flight: there will be crew caught up n this well if BA 78 didn't run. Are they effectively stuck there until 5th April?

No, they were going to be working out and coming home as passengers, and another crew doing it the other way round.

There's an "IDEN" button on transponders that highlights a particular aircraft to ATC - they'll often ask "Squawk IDEN" to get a highlight on their screens in periods of heavy traffic. I can't imagine ATC ever asking for a 7700, but maybe in other parts of the world?

Squawk ident, to be exact, rather than squawk iden...

According to the BA Source the 7700 squawk only appeared 'briefly' over France on the way back.

So there was no 24 rest with the crew staying down route? Fair enough

ATC can ask crew to select 7700 as it will show up through any suppressing filters on any radar screens, enabling all ATC other staff to see any 7700 squawk in any neighbouring airspace. This is helpful because it tells the controller not to try and contact them unless absolutely necessary.

Additionally, crews can sometimes select 7700 inadvertently on the way to selecting their intended squawk, however this is often not possible on the avionics most modern airliners have installed. It’s far more common on light general aviation aircraft, indeed I’d say around London it’s a daily occurrence. When I see 7700 come up on my screen for an aircraft not under my control, I wait at least 5 seconds before reporting it.

That's very interesting, thanks Heathrow Tower!

We ask for an IDENT to positively identify and validate the Squawk,usually just after take off when we validate that all of the information sent from the aircraft is correct e g altitude

We regularly ask for the 7700 if an aircraft is in an emergency so that all of the surrounding sectors can see that there's an issue-particularly to indicate that an emergency descent may be required

this is a very simple explanation

I heard it turned back as Ghana closed it's borders..

Correct.

I was alwyas taught to put into standby then change the sqwark code to avoid exactly that, Thought everyone did that, Seems not!

Sadly not!