SEATTLE — Alaska Airlines closed its $1 billion purchase of Hawaiian Airlines today, a day after the federal government removed the last major regulatory obstacle to the deal.

Alaska will also assume about $900 million in Hawaiian debt. Alaska says it will keep Hawaiian as a separate brand, eliminating the need to repaint planes.

To win approval from the Transportation Department this week, the airlines agreed to maintain current levels of service on key routes within Hawaii and between the island state and the U.S. mainland where they don’t face much competition.

Shares of Alaska Air Group fell a little more than 1% today.

The Justice Department, which had opposed previous deals between large airlines including JetBlue’s attempt to buy Spirit Airlines, has not challenged the Alaska-Hawaiian deal on antitrust grounds.

Alaska and Hawaiian also agreed to a handful of consumer protections, including not lowering value of frequent-flyer rewards as they combine their loyalty programs and promising to compensate passengers for cancellations and significant delays that are the carriers’ fault.

Seattle-based Alaska Airlines said those conditions were similar to its plans from the time it announced the deal in December.

The deal solidifies Alaska’s position as the fifth-largest U.S. airline by revenue.