Merger or Buy out? USAirways

I understand that anti trust laws prohibit companies to buy other profitable companies.
If USAirways was profitable, which I believe it was the last two years even though they are in debt, is United Airlines Aquiring USAirways by a merger or buy out?

As my fiancee works for US Airways, I hear a lot about this. This is the official statement:

Chicago, IL, and Arlington, VA, (May 24, 2000) - UAL Corporation [NYSE: UAL] and
US Airways Group, Inc. [NYSE: U] today announced that their boards of directors have approved a definitive merger agreement pursuant to which US Airways will be acquired by United in an all-cash transaction valued at $4.3 billion (plus the assumption of $1.5 billion in net debt and $5.8 billion in aircraft operating leases).

According to this, it is a merger. However, it still has to go through the anti-trust hearings and may not be allowed to happen since then American would want Northwest, Continental would want someone, etc, etc.