Expert: Mark Janus - 3/4/2011

Question
I recently viewed a four engined jet aircraft leaving a contrail looking like it had some sort of long pulse to it:

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This signature was from each of the four and all pulsating in sync. The contrail was from horizon to horizon. I could not make out the exact size of the aircraft, its color blended well with the sky color.

Any ideas????

Answer
Well I know of no commercial jet that somehow pulses its jet engines (especially four in sync)...so here is what I think you saw...  the atmospheric conditions have to be just right to actually see contrails (that persist)...  also in the atmosphere there can be a wavelike appearance (have you ever seen clouds that are lined up in rows).. now that part I can't quote what type cloud formation(s) those are...  well after the aircraft has past over and the air has settled back to its normal formation the contrails could/would get broken up into pieces (and yes they all would be broken at the same place...)  

I believe you saw contrails that where effected by the local atmospheric patterns... (updrafts and/or wavelike patterns)..

Thanx,
mj