Interesting...the United website has the following on the website. It appears to be an aircraft servicing issue. However, the .bomb also says that it is to go from SNA to LAX for crew reasons....

Flight

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Airline: United
Flight: 436
Date: Sun, Dec 20
Status: Not Departed
Aircraft type: Boeing 757-200
Miles earned: 1745

Departure

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Airport: Los Angeles, CA (LAX)
Scheduled departure: 10:32 AM
Estimated: 11:30 AM
Reason: Schedule change due to Aircraft Servicing
Terminal: --
Gate: --

Arrival

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Airport: Chicago O'Hare, IL (ORD)
Scheduled arrival: 2:37 PM
Estimated:
Reason: --
Terminal: Terminal 1 Concourse C
Gate: C25
Baggage claim: 10

Inflight

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Time enroute: 2 hour, 05 minute
Meal: Food for purchase
Entertainment: Movie