The 757's have been getting replaced for years now as newer stuff comes on stream
Mainly 319,320,321 and there are a few 767 that are shorter range and do services to European hubs..
They had had a new 320 in June just after that G-CPES left the fleet
There are two more 320's to come this month so I guess that will directly displace the remaining three which I think are actually two out of three at any one time... two service and a spare.
A 320 delivered in April saw I think it was G-CPEL go, so it does seem the latter days at least, have been direct one to one replacements with A.320's
This is all based on my observations.....internal politics may paint a different pic
There are some 747 to go in the next couple of months.......five due to be stood down at the end of September in fact.
Fourteen 767s are to go as the 787's get delivered so many of the other familiars will disappear, most noticeably will be the gradual reduction in the 747 fleet.
No mention though of the 737-400......they do a lot from Gatwick and seem to have a niche all to themselves at the moment, switching at times with Airbus A.319 wherever the capacity matches. Gatwick-Jersey sees A.319 most of the year with 737 in the summer, but at any time odd flights by the "other " type take place.
.G-CPEO,R,T..........G-CPES was in service until recently.
