James Bridle has been paying close attention to how different airports around Europe try to help Muslim travellers to find the direction to face Mecca:
[At the interfaith room at Athens airport…] The qibla - the direction which Muslims should face when performing prayer - is indicated by a green stripe on the floor, which terminates at the foot of a vertical strip of white light. This groove serves both as mihrab, the niche in a mosque that indicates the qibla, and a sort of surrogate Dan Flavin, pleasingly echoing both the "diagonal of personal ecstasy" and the Tatlin monuments. […]
On my last visit, however, there was evidence of discord. Just to the right of the qibla/Flavin, on the carpet and above the skirting board, twin arrows rendered in thick blue biro cross-hatching have been used to indicate a direction some ten degrees further south than the architect's stripe implies.
When you start to look for them, the qibla-scribblers are all over, as qiblas are apparently a contested part of interfaith chapels. In the Stille Rom at Oslo's Gardamoen Airport, two prayer mats lie alongside one another at angles to one corner of the space, but no qibla is evident, until, once again, you crouch down and peer at the floorboards, to find another set of arrows - this time in black biro - gouged into the woodwork. At least three different hands have been at work here, with another arrow in blue above the skirting board, and the word "قبلة," itself, in black again, next to it, to remove any doubt.
It turns out that the widespread use of smartphones may be contributing to the problem.