random aside but it happened to me the other week.
check in for LHR-ABZ 4pm flight and it was showing delayed an hour but was already at T5 and checked in like normal approx 2pm.
get continual updates of further delays and at one point it was showing delayed to 7pm due to late arriving aircraft (day of FR ATC strikes and weather)
so at 315pm i check and it stows ~7pm, fine. finish some work and just before i load up another tv show to watch on my laptop i make one last refresh of flightaware and now flt is back to deparitng at original time and boarding starts in ten mins!
so i scramble to get my stuff together and yes they swapped us from an inbound delayed VCY to an ontime RKV though were swapped from a319 to a321. i could only wonder how many people missed the flight because at T-90min it was showing a 3hr delay!