The pilot was talking with another crew member and apparently didn't realize that his microphone was on.
Southwest said Wednesday that the pilot was reinstated after going through diversity training. The incident happened in March and was reported this week by a Houston television station.
On a tape of the two-and-a-half minute rant, the pilot can be heard talking about wanting to socialize with co-workers but complaining that many were gay or too old or too heavy. Sometimes using profanity and slurs, he called them "a continuous stream of gays and grannies and grandes." An air-traffic controller in Houston told pilots in the area to check if their microphone was stuck open.
"The actions of this pilot are, without question, inconsistent with the professional behavior and overall respect that we require from our employees," said Southwest spokeswoman Brandy King. She said the pilot was reprimanded and suspended without pay, although she wouldn't say for how long. She said he apologized to air-traffic controllers and their bosses.
King declined to identify the pilot. She said he has worked for Southwest for more than a dozen years and has an otherwise good record.
The Federal Aviation Administration said it alerted Southwest after determining that the pilot on the tape was likely from Southwest.
FAA spokesman Lynn Lunsford said the incident occurred at a time in the flight when personal conversions are allowed in the cockpit but that the FAA "expects a higher level of professionalism from flight crews."