Updated 12:05 p.m.
A Southwest Airlines 737 with 139 passengers aboard landed safely Wednesday after experiencing a landing-gear problem and being forced into a holding pattern over the Central Valley for 3½ hours.
Flight 2547, to Chicago's Midway Airport, took off at 6:13 a.m. The pilot immediately notified tower personnel in Oakland that "we're having an issue with the aircraft ... we're going to need to return to the Oakland airport if we can get emergency return instructions."
When the tower asked the nature of the emergency, the pilot said, "It's an issue with our landing gear -- we don't know what it is yet."
Later reports suggested the problem was with the aircraft's landing gear -- and news reports suggested the issue may have been a blown tire.