Castlelake has assets under management worth £27bn ($36bn).
It entered talks in January with bankrupt US carrier Spirit Airlines over a possible takeover.
Castlelake has also previously bailed out collapsed Scandinavian Airlines (SAS) and then sold on its shares to Air France-KLM.
In interim results last month, EasyJet reported that bookings for summer flights had been lower than the same point last year because of uncertainty caused by the conflict in the Middle East.
It posted a half-year pre-tax loss of £552m ($700m), compared with a loss of £401m ($510m) a year ago.
