plane was flying from guangzhou , china to addis ababa , ethiopia .
boeing 777-300er was forced to land in mumbai the first time to refuel .
it departed but had to return due to engine trouble , indian media reported .
passengers disembarked and were transferred to a hotel .
what should have been a 10-hour flight turned into a day-long delay .
ethiopian was recently named one of the world 's most reliable carriers .