If you are travelling long-haul on United next month be sure to double-check your booking. United has had to suspend seven routes in June due to aircraft shortages. Suspended are EWR-OGG, EWR-HNL, EWR-NRT, IAD-GRU, IAD-GVA, IAD-HNL, and IAD-DUB. In addition, EWR-ARN is being completely discontinued (was to be summer-only).
The issue appears to be delays in getting United's Pratt-Whitney 777-200s re-certified. United has 19 "vanilla" 777-200s and another 29 777-200ERs still grounded after the uncontained engine failure back in Feb 2021. The planes were supposed to start coming back into service next week (after engine modifications and increased inspection frequency). That has been pushed back until the end of the month at the earliest.
United also has 22 GE-powered 777-200ERs still flying, but 48 grounded planes leaves a big hole.