Low aircraft oxygen levels

[Ramrod]

Just over half of all fliers analyzed had oxygen levels 6 percent lower than usual when the airplane was at maximum altitude -- a level at which doctors normally administer extra oxygen for hospital patients.

Link (http://edition.cnn.com/2005/TRAVEL/04/26/bt.oxygen.study/)

I detect some sort of cost-cutting........

[Xaccers]

Known this for ages, it's a common cost cutting exercise, but as you're sat inactive, you don't need as much oxygen anyway.
If you want you can ask them to ensure they have the right oxygen levels.

More of a concern is the longer than should be periods between airconditioning filter replacement, meaning you're getting gunky infection filled air being blown around the aircraft *yuck*