No, this was not intentional. In fact here is an article explaining the glitch and what possibly could have caused it ...
Source: Chicago Tribune
Window of blame opens on $5 United tickets
A few industry experts are suggesting that the Internet ticketing problem experienced by United Airlines on Tuesday may be tied to a problem with the carrier's computers--rather than the Airline Tariff Publishing Co..
Airline Tariff Publishing of Herndon, Va., was created in the 1960s to independently handle the transmission of fare information to travel agents and reservations systems.
The company now also transmits the data to a variety of booking sites, including that of United.com., because of federal regulations.
"We got the information [on United fares] correctly from ATPCO into our system," said a techie who helps run a competing Internet booking engine.
United officials have said the error was caused by the publishing company.
It is the third time in a little more than a year that United has inadvertently allowed customers to buy heavily discounted tickets. On Tuesday, nearly 1,000 round-trip tickets were sold for $5, plus various government taxes, during about 51 minutes over the lunch hour, said Rono Dutta, United's president.
Its better to be on the ground wishing you were in the air than be in the air wishing you were on the ground. Fly safe!