PHOTO: Phoenix Sky Harbor International Airport at night. (photo via Flickr/Patrick Emerson) A fire alarm prompted more than 40 Phoenix-bound flights to be diverted across the Southwest over the weekend.According to The Arizona Republic, 46 flights en route to Phoenix Sky Harbor International Airport were diverted after a fire alarm went off in an air traffic control tower Sunday morning.The tower was evacuated as a precaution and the incoming flights were diverted to nearby airports, including Tucson; Las Vegas; Mesa; Albuquerque; Burbank, California and Ontario, California, airport spokeswoman, Julie Rodriguez, confirmed.The Phoenix Fire Department responded to the alarm around 8:45 a.m. local time Sunday. Officials determined that the alarm was triggered by a malfunctioning air handler sensor.ABC 15 reported the sensor was off-gassing steam, which caused the alarm to sound.READ MORE: Ryanair's Flight Cancellation FalloutThe affected flights were headed to Phoenix by 10 a.m. Sunday.Flights arriving again @phxskyharbor 40+ inbound diversions this morning after @FAANews Tower evacuated due to alarm. Now resolved.— PHX Sky Harbor (@PHXSkyHarbor) September 24, 2017According to flight-tracking website FlightAware.com, 177 flights originating at Phoenix Sky Harbor were delayed Sunday. The figure represents approximately one-third of Sunday's scheduled flights from the airport.Follow @_Pat_Clarke