Re: In the air?

Date:         28 Mar 98 14:21:47 
From:         kls@ohare.Chicago.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
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>That brings up an interesting question, how do airlines schedule big
>maintenance events such as D checks?
...
>Assuming that SwissAir doesn't have a spare MD11 sitting
around, what happens if this plane needs maintenance.  Is SR110/111
canceled?  Do the lease a plane for a week?

A D check takes a lot more than a week.  I think a C check is usually
scheduled for about two weeks, with a D check taking at least a month.

Anyway, one case is an airline with a relatively small fleet flying a
lot of long, international routes.  United's 747-400 fleet, for example.
During past summers, UA has had them scheduled absolutely solid, with
no opportunity for anything beyond routine line maintenance (up to a B
check, which takes about 12 hours and occurs roughly once per month).
Once the summer schedule is over, many routes are trimmed back (SFO-NRT
has operated with three daily flights in past summers, but only two for
the remainder of the year) or switched to smaller equipment (one year,
UA used a 747-400 for ORD-FRA but just for the summer).  At this point,
there are spare 747-400s and so it's no problem rotating them through
lengthy maintenance.

Another case is a very large fleet, such as UA's 737-300 fleet, which
totals 101 aircraft.  With that many aircraft and two weeks for the
annual (actually every 393 days) C check, there should be four aircraft
in heavy maintenance on a nearly continuous basis, so the fleet plan
includes spares.

There undoubtedly are situations where an airline has a fleet that's so
small, they must lease a plane while theirs are in for heavy maintenance,
but I'd guess Swissair just does their MD-11s during the winter months.

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