The link is "top priority" in a report which also looks at securing income, increasing passenger numbers and creating new routes.
A longer-term vision for the city airport could involve companies working in offshore renewable energy and securing other routes, such as to Amsterdam.
Transport Minister Keith Brown said: "Securing the future of the service between Dundee and London is the top priority.
"This study also highlights a number of commercial opportunities, like engaging with companies in the offshore renewables sector, which could give Dundee Airport a unique place in Scotland's aviation industry."
Short-term recommendations such as retaining London flights and boosting passenger numbers are estimated to cost between £125,000 and £150,000. The cost of medium-term initiatives, such as expanding business links and air routes, is around £250,000 in each of the following two years.
A "modest investment" would be needed to make the airport suitable for helicopters if it is to be positioned as a construction and servicing base for wind turbine projects off the east coast, the report states. Subsidy levels are estimated at about £2.7 million a year and could rise to £3.5m if CityJet withdraws its London City service.
Business traffic is growing, the report shows.
Attempts to get other airlines interested will require persistence, the report adds. "Dundee is not an easy 'sell' but if the issue of whether there is a market to be served at all is to be bottomed out once and for all, there is a requirement for this effort to be given appropriate priority and funding," it notes.
Inglis Lyon, managing director of operator Highlands and Islands Airports, said the Dundee hub has competitive challenges.
"However, there are opportunities which we are currently pursuing to attract new business to the airport, including renewables and general aviation, and efforts to attract new scheduled services continue," he said.