[alarm rider]

I was an MTI, and even though the picture shows matress covers, I would not have let a flight go until those matress covers were tight.

[Iron Munro]

I was an MTI, and even though the picture shows matress covers, I would not have let a flight go until those matress covers were tight.

Upon a closer look I believe you are corect.
It almost looks as if it they are unassigned bunks or a barracks for transients.

Of course, we all know that the correct nomenclature for mattress cover is F**T Sack.