And aren't United renting slots from Aer Lingus at Heathrow at the moment.
In fact United (old Continental Airlines side) are indeed leasing two pairs of slots from EI and BA are leasing another pair. This was said by Dermot Mannion during the time of the SNN LHR bother. It's believed that BA may have another pair belonging to EI and there's another pair leased to another carrier ........ someone said Northwest before so I guess Delta now.