The Scottish Citylink service, which operates round the clock, has been upgraded to double deckers, which will increase seats by one third.
The link launched in 2013 and saw a 23 per cent increase in passengers last year.
Introduction of the five new coaches, with more legroom and luggage space, comes as Glasgow Airport continues to haemorrhage passengers, mainly because of major Ryanair route cuts last year.
The airport no longer publishes figures, but the latest available Civil Aviation Authority data shows its August total was down 10 per cent on last year to just under 910,000. Edinburgh’s total was up 0.5 per cent to 1.48m.
Glasgow expects to lose 600,000 passengers this year, ending with 9.1m, while Edinburgh is growing towards 15m.
Edinburgh has dozens of Ryanair routes compared to seven in Glasgow, and the capital’s airport has more destinations in northern Europe.
Glasgow has 120 destinations against Edinburgh’s 157.
Edinburgh Airport chief executive Gordon Dewar said: “Citylink’s investment in these new coaches delivers a journey that is as easy and comfortable as possible, and one that also provides wi-fi and charging capabilities so people can keep up to date with their flight or even work on the way to the airport.”
Scottish Citylink operations director Peter Knight said: “These vehicles deliver extra capacity and game-changing amenities that we believe will lead to an even more enjoyable travel experience for our customers.
“By providing greater convenience, a more comfortable journey and improved on-board technology, we look forward to attracting even more people on to our services.”
A spokesperson for Glasgow Airport said: “2019 has been a challenging year for regional airports across the UK.
“However, we’re looking forward to 2020, which will see the addition of a host of new services. Lufthansa has confirmed its popular Frankfurt route will increase to double daily in March and TUI will operate what will be its largest-ever holiday programme from Glasgow, with the addition of almost 200,000 seats.
“EasyJet will also introduce a fifth based aircraft in March, which puts Glasgow Airport on a course for future growth.”