Two of the most-watched mergers undergoing antitrust scrutiny are close to winning approval by U.S. competition enforcers--Alaska Air's (ALK - Get Report)  $4 billion plan to acquire Virgin America (VA)  and Dow Chemical's (DOW) pending $130 billion purchase of rival chemical conglomerate DuPont (DD - Get Report) .

Under an agreement with the DOJ, Alaska Air is free to close its acquisition of Virgin America, on Monday, Oct. 17, absent a legal challenge from the Department of Justice, which has been reviewing the deal in-depth since May.

There has been some speculation that the DOJ is concerned the merger will harm competition among airlines serving the West Coast, particularly at airports serving Los Angeles and San Francisco and might challenge the transaction. With expiration of Alaska Air's agreement not to close the transition expiring Monday, nervousness over the DOJ's concerns caused Virgin shares to drop in early trading Friday, but the stock rebounded late in the day as it became clear the DOJ would not challenge the transaction ahead of the deadline for approving the deal.

Alaska Air officials did not respond to a request for comment Friday but the airline is not expected to close the transaction without clearance. The two sides continue to talk about the DOJ's concerns and Alaska is expected to forgo consummating the merger until the government is ready to let the deal go forward, which could come as soon as Monday.

DOJ officials declined to comment.

As for Dow's acquisition of DuPont, Bloomberg reported Friday that Dow is trying to sell a unit that makes copolymers used in food packaging. A sale of the unit would be the first of several divestitures necessary to win the DOJ's approval. Launching the sales process is a strong indication that Dow is confident that antitrust clearance will be forthcoming.