I was looking at flights from DEN -> MEM, and saw this extra-long route that FDX1311 took last night (9 Aug 2021) FDX1311 DEN-MEM 9 Aug 2021

Thinking they were probably just avoiding storms, I scrolled down and saw there were 3 other DEN-MEM flights under that flight number, all which also took the same extra-long route.

FDX1311 DEN-MEM 5 Aug 2021 FDX1311 DEN-MEM 29 Jul 2021 FDX1311 DEN-MEM 26 Jul 2021

What's the purpose of this extra long route? It's more than double the straight-line distance!


1 Answer 1



FDX1311 is a daily scheduled flight, called a flying spare, or more colloquially a sweeper. It's a provision to remedy unplanned events which would otherwise prevent customers shipments to reach FedEx Memphis super-hub before dawn, and eventually to prevent shipments to be delivered in time.

Fedex sweep flight 1311

Fedex sweep flight 1311, Youtube

Route and reuse after landing

The flightpath is designed to allow the aircraft to be diverted to several airports in the US south area where FedEx has an important activity. When reaching Memphis airport, the aircraft becomes available for dispatching shipments from the hub.

Use cases

FDX1311 is part of FedEx contingency plan which, according to Fortune, comprises five aircraft to cover the whole US territory (to be compared to the 600+ aircraft fleet).

Diversion is triggered in quite different cases:

  • To fix unplanned maintenance. Aircraft availability and safety involves preventive maintenance and unavailability is well scheduled. But unplanned failures or damages still occur, some shipments can be left without a carrier. The spare aircraft will fix this problem.

  • To fix volume prediction errors. The number of containers can be predicted as soon as the shipments are collected, and aircraft can be dispatched accordingly for the next 24 hours. However there can be mistakes. Mistakes involving large volumes/weights cannot always be fixed with the planned aircraft. Containers in excess may be left at the warehouse. They will be collected by the spare flight.

  • To collect forgotten shipments. Errors may occur during containers preparation or loading into the holds, resulting in customers shipments forgotten or wrongly dispatched. The spare aircraft will get take them to Memphis in time.


According to FedEx each flight costs $30k. Most of the time it just flies this route empty or lightly loaded. Fuel consumption is about 30% higher than for the direct path.

Cost/benefit ratio

Individual customer shipments may experience delivery delays without large consequences, or without strong reaction. This is not the case for large customers for which contracts definitely include a delivery delay commitment, associated penalties and contract termination clauses for service failures.

I guess this $30k a day investment for this region is the quality assurance response to the evaluation of risks above, and those I'm not aware of. This is good for image, for competitiveness and for contracts renewal.

  • 5
    $\begingroup$ @757toga I would guess the commercial implications are higher for freight carriers. If a few hundred units of self-loading cargo get delayed somewhere by a few hours, you pay the minimum legal compensation and that's the end of it. On the other hand, losing a long-term freight contract with a large company that is worth millions of dollars a year, because you screwed up too often, is a different scale of problem. $\endgroup$
    – alephzero
    Aug 11, 2021 at 0:20
  • 4
    $\begingroup$ @alephzero self-loading cargo - euphemism of the day. FedEx has the ultimate hub & spoke system, one which "self-loading cargo" wouldn't approve of. If FDX1311 takes a quick stop at DFW, yes it might be some high-value pharmaceuticals or electronics from big companies. It could also be a bunch of legal paperwork from small local law firms or last-minute gifts (think Mother's Day or Xmas, though those are seasonal, not every day). FedEx plans for these contingencies. The rest of the freight doesn't mind the extra 2 hours in the air, and a possible pit stop. Unlike "self-loading cargo." $\endgroup$ Aug 11, 2021 at 1:08
  • 13
    $\begingroup$ @mins So more a cargo air patrol (CAP) :-) $\endgroup$
    – Dohn Joe
    Aug 11, 2021 at 10:54
  • 6
    $\begingroup$ Thanks for the amazingly detailed answer! I'll admit being a bit ashamed that it seems simply googling the flight number would have led me to an answer, but you consolidated in your answer a fair amount of pieces of information from various sites. Thank you! $\endgroup$
    – Ziwcam
    Aug 11, 2021 at 17:48
  • 1
    $\begingroup$ @mins - Yes , aircraft unplanned maintenance and parcels left behind by the regular aircraft" part pls. $\endgroup$ Aug 12, 2021 at 6:39

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .