Shares of the Chicago company were down 1.5% to $57.58 in premarket trading.
For the quarter, United Air in a regulatory filing pegged revenue at $3.2 billion, down 66% from the year-earlier quarter. United earlier had forecast that revenue would fall 65% to 70%.
The FactSet consensus of Wall Street analysts had called for $3.35 billion in revenue.
In March, the company said it saw "a forward acceleration in customer demand for travel and new bookings, resulting in positive average daily core cash flow" for the month and "expected positive average daily core cash flow moving forward."
The company said it had $21 billion in available liquidity as of March 31, including $7 billion under the Cares (Coronavirus Aid, Relief and Economic Security) Act loan program.
Meanwhile, United said it intended to begin a private offering to eligible purchasers of $5.5 billion of senior secured notes. One tranche is due 2026 and the other in 2029.
United will use the proceeds, together with its credit facilities, to refinance its existing revolving-credit line, a 2017 term loan and its Cares Act loan.
United was upgraded to equal weight from underweight, and Alaska Air went to overweight from equal weight.
Earlier this month, news reports indicated that United was planning to begin hiring about 300 pilots as more people were vaccinated and demand for travel increased.
The airline industry was battered by the COVID-19 pandemic as businesses closed, consumers were locked down at home, and travel collapsed.