That followed the midair blowout on one operated by Alaska Airlines earlier in the month.
The two carriers are the main operators of the affected type.
But the drama hasn't stopped United feeling bullish about the year ahead.
On Monday, it predicted adjusted profit for this year at up to $11 per share - well ahead of analyst forecasts.
United says travel demand remains strong, and is expected to keep growing.
It's also benefiting from strong demand for premium tickets following the end of health-crisis lockdowns.
Fourth-quarter profit also beat forecasts.
Shares in the airline rose around 8% in after-hours trade following the outlook.
United does, however, anticipate a short-term hit over the MAX crisis.
It expects losses to be wider than previously thought over the first quarter due to the grounding.
U.S. aviation watchdogs have said the planes will remain on the ground until they are proven safe to fly.
United operates 79 examples of the MAX 9, and many more of an earlier model that is also subject to checks.
