Narrative:

I was working sector 70 and got a hand off on a B737 who had been given a reroute by the previous sector. The B737 checked in and complained about the reroute and so I checked on the reasoning and gave the B737 an explanation. The B737 made no statement of 'minimum fuel' or 'emergency fuel' whatsoever. I had been watching the B737 and another air carrier from 8 minutes and determined that they were fine; at 8 minutes I showed 7.2 miles. At 4 minutes I showed 6.5 miles with the B737 slowed some. I assumed it was our normal target jump/speed flux areas. At 2 minutes I showed 6.1 miles with the B737 slowing more approximately 30 KTS; but it was still good. At approximately 100 seconds out; the B737 called and said 'we have slowed to .76 for fuel.' I told him I needed him to maintain normal speed; because another air carrier was going 6 miles behind him in 2 minutes. The B737 said 'unable' so I immediately descended the B737 to FL360. The B737 said unable to the descent to FL360 due to fuel. Out of time; I turned the other air carrier 20 right to assure separation with the slowed B737. I also was able to get the B737 to speed back up to his 'normal' speed of .79 mach for a short amount of time after this and re-assigned FL380. I later gave the B737 the local phone and he called our supervisor. The issue is the B737 slowed considerably with out approval. Recommendation; the 7110.65 doesn't say pilots can change their speed with out telling us; nor do the fars; or the pilot/controller glossary. According the supervisor who took the call from the B737; the pilot thought he could change speeds. The only thing I have found is in the aim; 4-4-12 says on and adjusted speed; pilots are expected to maintain a speed within 10 KTS or .02 mach. I believe this range is clearly for pilot skill level; and aircraft performance. This in no way allows pilots to fly speed within 10 KTS or .02 mach at their discretion that would be ridiculous.

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Original NASA ASRS Text

Title: ZAB Controller described a near loss of separation event between two enroute aircraft at FL380 when one aircraft elected to reduce speed for fuel concerns failing to notify ATC.

Narrative: I was working Sector 70 and got a hand off on a B737 who had been given a reroute by the previous sector. The B737 checked in and complained about the reroute and so I checked on the reasoning and gave the B737 an explanation. The B737 made no statement of 'minimum fuel' or 'emergency fuel' whatsoever. I had been watching the B737 and another Air Carrier from 8 minutes and determined that they were fine; at 8 minutes I showed 7.2 miles. At 4 minutes I showed 6.5 miles with the B737 slowed some. I assumed it was our normal target jump/speed flux areas. At 2 minutes I showed 6.1 miles with the B737 slowing more approximately 30 KTS; but it was still good. At approximately 100 seconds out; the B737 called and said 'we have slowed to .76 for fuel.' I told him I needed him to maintain normal speed; because another Air Carrier was going 6 miles behind him in 2 minutes. The B737 said 'unable' so I immediately descended the B737 to FL360. The B737 said unable to the descent to FL360 due to fuel. Out of time; I turned the other Air Carrier 20 right to assure separation with the slowed B737. I also was able to get the B737 to speed back up to his 'normal' speed of .79 mach for a short amount of time after this and re-assigned FL380. I later gave the B737 the local phone and he called our supervisor. The issue is the B737 slowed considerably with out approval. Recommendation; the 7110.65 doesn't say pilots can change their speed with out telling us; nor do the FARs; or the pilot/controller glossary. According the supervisor who took the call from the B737; the pilot thought he could change speeds. The only thing I have found is in the AIM; 4-4-12 says on and adjusted speed; pilots are expected to maintain a speed within 10 KTS or .02 mach. I believe this range is clearly for pilot skill level; and aircraft performance. This in no way allows pilots to fly speed within 10 KTS or .02 mach at their discretion that would be ridiculous.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.