I did a search and only found older info on a few airlines. What I'm wonder is how many and of what kind of airplanes do airlines keep in back up for active use and also in "cottonballed" status as a FA referred to them once.

For example how many usable aircraft and and what kind do UA and CO individually have on call. Also if known how many in long term storage. I've been curious about this for awhile. I figure within the US CO has a few spare 737s but probably not a half dozen 777s hanging out and IAH and EWR. Not looking for speculation rather looking for some hard numbers.

This is a good starting point:

http://www.planespotters.net/Airline/index.php

Follow the links...

Henry,
I took a look and it seems almost none of the airlines I selected has any airplanes in storage which makes me curious about the validity. I checked the major US airlines and only USAir had any planes in storage. This is plausible as it costs money to keep them and are typically older aircraft. But I'm more interested in excess/standby active airplanes.

Edit: thanks for the info btw.

You are aware, I'm sure, of the storage facility in Mojave, California. I've passed by there many times on my way to the US Borax mine a bit to the east.

Yes I've read up on some of the "graveyards" but I'm more into the reserve craft for functional use. Like if an engine goes back on a 772 do they even have 1 or 2 extra in line that isn't scheduled every day.

They do, but it really varies day by day. That means no one plane is used as reserve only, as parking in any airport is expensive,

At least in the US, aircraft leasing is very common. (I learned about this in a Financial Statement Analysis text.) The physical aircraft flown by US airlines are in many cases owned by leasing companies, which can spread them around as needed, taking advantage of a pooling effect. Storing "backup" aircraft would be incredibly financially inefficient for individual carriers.

Sorry, I don't have the hard numbers you seek, but a google search for "aircraft leasing" should get you started.

most carriers with a fleet of 20+ planes will not employ all aircraft on scheduled flights. Usually a 'hot spare' will be parked in the airlines base hanger (less charges) and used if another plane goes tech.

the same goes for long haul carriers where a spare 777, 340etc will be on standby.

Very rarely is a particular airframe used as the spare. A schedule is however built to maximize the degrees of flexibility as to which particular airframe can be used for any particular flight. eg. If you have 3 planes each flying 8 hours a day, you theoretically can schedule them so that there are 2 planes backing up the third plane at all times (in practical terms however you will almost certainly have less, especially in a hub-and-spoke model).

There are other variables of course such as scheduled maintenance downtimes, parts and labour availability, etc.. but there is an entire science of scheduling which works to accommodate these and optimize utility within a set of constraints while still maximizing the operational flexibility.