reply to post by akrasia
No prob...here to keep the record straight.
Here's another good source for you, to explore and see the types of established high-altitude routes that exist, especially over LAS:
I can't seem to link directly to the page I want, on that site.
SO...I'll walk you through it --- open the website, and you will see the Los Angeles area VFR aviation sectional chart (I've noticed that sometimes,
depending on your computer, the site might know your area, and center you in your ISP home town...not sure how it does that...)
Anyway, if it's not showing LAS, then look upper left corner, type in KLAS, click 'Go'. ("KLAS" is the ICAO code for McCarren Airport). NOW you
will see the VFR sectional for the Vegas area.
Along the top are some tabs, to select other charts --- click on "Enroute H-4". The 'H' is for the High-altitude IFR charts, the ones jets use
All of those black lines, with numbers in boxes, are the Jet Airways...the defined routes between VORs, intersections and waypoints. (The blue ones
are a fairly new depiction, for airplanes using GPS exclusively, when equipped and qualified...it's part of the upgrade for the future...called
"Free Flight"...to help reduce delays and congestion problems).
Notice how the Jet routes angle, compared to each other.
The LAS VOR, due to its location, is very heavily traveled by many flights, on many different city-pair departure/destinations. You see it is part of
Also, remember the "winds aloft" forecast?? Every contrail, once formed, will "drift"...) along with the prevailing winds, for as long as it
lasts. Just like the clouds do.
ALSO, keep in mind, that airliners are NOT required to always follow the Airways exactly. For example, if I'm flying a trip from LAX to JFK, the
flight plan is often going to be along J-9/100/146, passing right over the LAS VOR. (Multiple numbers merely mean two or more Jet Airways co-exist
between two points for a short while, before diverging later).
But, farther down the way, there are bends in the route....(because, as noted, Airways are "point-to-point, a holdover from years ago...hence, the
new "Free flight" concept beiing developed...). Farther to the northeast, along a typical routing to JFK from LAX, is another VOR...named "Bryce
Canyon" (BCE). It's in Utah. (Look on chart "H-3").
Air traffic control (ATC) may, on request, or on their own...for traffic conflict reasons, etc...clear flights "direct" down the route, to other
points further in their flight plan...to "straighten out" the routing, move them out of others' way, etc. (We really like the direct
clearances...it gives the impression we're getting a "short-cut"...but the time savings are minimal, actually...still, fewer turns, more
comfortable for passengers....)
Oh, and....I think you were shown the link to flightaware.com...
already. On that site you can look up every flight that's in the FAA ATC
computer system, with IFR flight plans, and see the actual filed routing info.
Let's take a look at a typical LAX-JFK flight selected at random, from today: flightaware.com...
I grabbed that one, for no particular reason.
In the box with the info, is the flight plan routing. This is it:
LOOP4 DAG J100 LAS
BCE J60 IOW OBK J584 CRL J554 JHW J70 LVZ LENDY5
I bolded 'LAS' there, for you....that plan was the "Loop Four" (LOOP4) departure (SID) from LAX. To the DAG VOR, Jet 100 to LAS, then direct BCE
(all VORs are a three-letter code), Jet 60 to IOW, etc, etc.
It's quite common to request a 'direct' to IOW (Iowa City) as we near our cruise altitude...and that direct routing, depending on whne/if it is
granted, might mean we pass ABEAM the VOR at Vegas...not directly overhead.
SO...long-winded way to describe WHY contrails can seem to be so varied. Routings, changes in routings, and winds....just a few to consider. As you
see, it's complicated, at times.
Anyone interested in aviation might enjoy to learn a bit, from this info posted.
[edit on 26 July 2010 by weedwhacker]