2/10 UA934 EWR-LHR 763 took off, got as far as Maine and then turned back to EWR. Now delayed 10h30min due to aircraft maintenance - also interestingly they're swapping out the original 2-class 763 for a 3-class bird... some pax will not be happy

2/9 UA930 SFO-LHR 772 delayed 3h due to operational difficulties

also must have missed this amidst all the snow-related cancellations:
2/8 UA1 SFO-SIN 789 cancelled due to aircraft maintenance
2/10 UA2 SIN-SFO 789 cancelled due to aircraft maintenance