The rail link was to have opened in time for the Commonwealth Games
The managing director of Glasgow Airport has warned that if the proposed rail link is cancelled other transport improvements must be made a priority.
Amanda McMillan has written to all MSPs ahead of Holyrood's budget vote which is expected to axe the £300m project.
She said the rail link remained the airport operator's favoured option.
A Scottish government spokesman said it had to take the difficult decision to remove the scheme from the proposed budget due to Westminster cuts.
He added: "Despite these Westminster cuts, the Scottish government remains committed to delivering policies and infrastructure that will make a significant contribution to this country's sustainable economic growth and we look forward to continuing our working relationship with the airport owner to deliver these aims."
The spokesman said through Transport Scotland it was working closely with the airport operators, BAA, and others to "identify further enhancements to Glasgow's transport infrastructure to improve connections across the city".
Ms McMillan said she was worried that by dropping the rail project it would leave "a gaping hole" in road and rail access to an economic hub of "national importance", and that taking no other action was not an option.
She added that ground links to the Renfrewshire airport were "frustrating" for passengers, particularly on the M8.
Ms McMillan also made the case for Glasgow Airport as a key economic driver for all of Scotland, with 5,000 jobs at the airport and more than 100 companies on site.
The managing director said Glasgow was Scotland's principal long-haul and transatlantic gateway, providing a vital platform for the inbound tourism industry, as well as a gateway for Scots leaving on holiday.
'Playing its part'
In her letter, she writes: "If passengers cannot easily access Glasgow Airport, they will choose another airport.
"Unless action is taken to address this serious challenge, the reputation of our airport and our ability to attract passengers beyond metropolitan Glasgow will be seriously damaged.
"Ultimately this has implications for business, tourism and employment throughout Glasgow and Scotland.
"If the Glasgow Airport Rail Link (GARL) is to be cancelled, it is essential the Scottish government considers other measures to improve access to Glasgow Airport, and safeguard resources to ensure these improvements can be delivered."
Ms McMillan said the airport's owner was committed to playing its part, and to help fund a comprehensive review of its surface access needs.
"The cancellation of GARL cannot be an end to the matter. A serious challenge remains - how to ensure continued access to an asset on which our nation's economy depends. Doing nothing is simply not an option," she added.