The last Continental Airlines flight takes off tonight, and the airline that was once one of the nation’s biggest will all but disappear into United Airlines.

United and Continental, which both fly to Hawaii, merged in 2010, but passengers almost could have missed it. The big change occurs early Saturday when United combines passenger reservation data from both airlines into one massive computer system. That means one frequent-flier program and one website. Tickets will be issued under United’s name only.

The airline will stop using Continental’s "CO" code. That means no more Continental Airlines tickets, or flights — even though the Continental name is still on some planes.

The names of both airlines have been on signs at gates at its 10 hubs. By Saturday, "Continental" signs at all 372 airports it serves will be gone.

Until now each airline issued its own tickets, and passengers had to use separate ticket counters. On Saturday it will no longer matter which counter passengers go to. Gate agents should be able to book travelers on flights across the combined airline.

The systems are combining under the name of United’s MileagePlus frequent-flier program. Travelers who have accounts at both airlines will essentially be credited for their Continental OnePass miles in their combined MileagePlus account. But their MileagePlus account numbers will be those from OnePass.

As for passwords, PIN numbers and addresses, some of those will transfer and some won’t. United has emailed frequent fliers the details. United.com becomes the website for the combined airline, but its look is the old Continental.com. The websites are set to go dark at 2 a.m. EST Saturday. United is aiming to have the switch done in time for travelers to check in for 6 a.m. EST flights.