First interview was via phone with HR, a few days later I had a phone interview with the hiring manager. One week later I had a 1:1 in person interview with the hiring manager and on the same day a small panel interview with 3 other people on the team. Offer came a few days later, which required a drug test, criminal background check and a employeer check.
Note: Many interviews/offers do not happen that quickly at United, also their background check differs based on the position.