On Sunday, United Continental Holdings announced it will invest more than $500 million in upgrades, giving customers a tangible sign that the recently fused airlines are emerging as a newborn fleet.

 In Sunday's announcement, the airline revealed its plans to install premium-class seats, expand overhead storage space, roll out new inflight Wi-Fi and entertainment systems, and renovate older planes.

United Continental will nearly double the overhead storage space on over 150 aircraft - making it possible to store 30 to 40 more rolling bags per flight - and add flat-bed seating on 62 additional long-distance planes. The Wi-Fi will be installed on more than 200 aircraft and the company will stream wireless video on its 747-400 aircraft.

In total, if the upgrades go as planned, United will have more flat-bed seats than any other U.S. airline and more extra legroom economy seats than any other airline worldwide.

The remainder of the $550 million will be aimed at creating a consistent customer experience that combines the most popular offerings of both carriers.

All this is on top of the 25 new aircraft the company will introduce next year, including the recently unveiled Boing 787 Dreamliner.

The overhaul is expected to be complete by 2013, though costumers can expect to see some of the changes as early as next month.

Currently, United Continental is still working on a new boarding process, integrated check-in kiosks, combining frequent-flier programs and onboard snack menus.