Southwest passenger's video shows plane's engine spitting out flames mid-flight

• A Southwest Airlines plane left a trail of flames in the sky after taking off from Houston, Texas. 
• It returned to Houston's Hobby Airport 27 minutes after departure because of a "mechanical issue."
• One passenger said he could see "fireballs shooting out" of the engine from his window. 

A Southwest Airlines plane was seen on fire in the sky shortly after takeoff from Houston, Texas, video shows.