Google may face an antitrust lawsuit by the US Justice Department over its $700m acquisition of ITA Software.
The acquisition is crucial to Google's plans for a service to handle airline-related questions, such as flight prices, times and availability and to display this information in search results.
The DoJ has not made a final decision about whether to block the purchase by Google, according to US reports citing anonymous sources.
Google announced plans to acquire the airline flight and ticket information company in July, but online travel companies including Microsoft and Expedia are opposed to the deal because of concerns that Google will prevent others using ITA's technology.
The National Business Travel Association has expressed concerns that the deal could result in higher costs to business buyers and hamper access to real-time airfare information.
But Google has said the acquisition will increase competition and has undertaken to license the ITA software to third parties after the acquisition is complete.