The Scottish winger looked like he was heading to Marbella.
Celtic are in Europa League action this week, taking on Molde of Norway in their third group match so far.
The Bhoys currently sit in second placed, just two points behind table topping Molde in their group but will go into the game confident after narrowly throwing away wins against both Ajax and Fenerbahce in their opening fixtures.
Celtic's players flew out today to face Molde, who appointed former boss and Manchester United legend Ole Gunnar Solskjaer in the management role today, with one of the first-teamers choosing some rather interesting footwear for the journey.
Perhaps winger Gary Mackay-Steven has been lied to by his team-mates and told they are playing in Spain this week because he turned up for the flight in flip-flops!
It caused quite a stir on twitter with many fans channeling their inner Kyle Lafferty to poke fun at the former Dundee United star:
Surely Gary Mackay-Steven has lost some sort of bet given his choice of footwear here. pic.twitter.com/7szctlsWcU— Kieran Caw (@Kieran_Celtic) October 21, 2015
Gary Mackay-Steven, I got 1 question for ya.... WOT R THOOOOOSE?! pic.twitter.com/5t1fLdnw92— Jon Ross Turnbull (@JonRossT) October 21, 2015
You would have thought Gary Mackay-Steven is jetting off to the Caribbean with his choice of footwear. pic.twitter.com/ZVDUu4Tuy9— Read Celtic (@ReadCeltic) October 21, 2015
I once saw Gary Mackay-Steven in Celtic trackies and flip flops So I bought Celtic trackies and flip flops— Brucie Bonus (@Brucehillbhoy) October 21, 2015
Perhaps one of his team-mates, or indeed his Norwegian manager, would be kind enough to inform him that the weather in Molde is not much different to that in Glasgow. In fact, it is about a degree or so colder!