Shares of the Chicago air carrier at last check were down nearly 1% to $252.30.
United informed staff of the hiring on Thursday, according to an internal email reviewed by CNBC.
"With vaccination rates increasing and travel demand trending upwards, I’m excited to share that United will resume the pilot hiring process that was halted last year,” Bryan Quigley, United’s senior vice president of flight operations, said in the note.
“We’ll start with the approximately 300 pilots who either had a new hire class date that was canceled, or who had a 2020 conditional job offer."
United is the first of the large U.S. carriers to announce it will resume pilot hiring.
Last week, the airline said it would add more than two dozen new flights to its domestic schedule starting Memorial Day weekend.
United recently said it expected core cash flow to be positive in March, as customer demand for travel and new bookings had improved from earlier estimates.
The airline industry was devastated by the COVID-19 pandemic shutdown. Airlines urged thousands of workers to take buyouts, early retirement packages and leaves of absence as they raced to cut costs during the pandemic.
U.S. airlines together lost $35 billion last year but expect a steady rise in bookings as more of the public is vaccinated and feels more comfortable getting on planes.
The Transportation Security Administration screened an average of about 1.2 million people per day last month, up 15% from a year ago when the pandemic and stay-at-home orders halted almost all travel.