** United Airlines UAL.O shares rise 6.4% to $71.30 premarket

** Airline warns of profit risks if US economy falters, but says its forward bookings over the last two weeks have remained stable

** United's Q1 profit came in at 91 cents/shr , topping analysts' expectations of 76 cents/shr –its first March quarter profit in five years, according to data compiled by LSEG

** Shares of other carriers also rise, Delta Air Lines DAL.N up 2.9%, Southwest Airlines LUV.N up 2.6%, American Airlines AAL.O up 1.2%

** United holds a trailing 12 months PE ratio of 6.26 vs industry median of 4.59

** It expects to hit its FY profit forecast of $11.50 to $13.50/shr, given the demand environment remains stable and fuel prices stay around their current levels

** Peers Delta and Frontier Airlines ULCC.O previously withdrew their FY forecasts

** YTD, United Airlines down 31% vs 8.3% fall in the S&P 500 index .SPX

(Reporting by Abhinav Parmar)

((abhinav.parmar@thomsonreuters.com))