Re: [Fwd: Flight from San Francisco to New York]

[Rondo JEFFERY <RJEFFERY@WEBER.EDU>]

Re the time of flights from west coast to east, and vice versa--
   The first thing to remember is that the times given in the flight
schedules are LOCAL times.  That means when determining the time of
travel between San Francisco and New York City, for example, you have
to add or subtract three hours, depending on which way you are going.
   The second factor is the trade winds.  Anyone who has flown cross
country can tell you that it takes less time going west to east than
east to west.  The reason is that the planes fly at about the same
speed relative to the air.  And the air aloft (at roughly 35,000 feet,
where airliners fly) is almost always from west to east, and about 100
mph.  The ground speed is therefore higher going west to east than
vice versa.
   I checked the Delta Airlines flight schedule on the WWW just to
get some numbers to put in this reply.  A non-stop from SFO to JFK
shows as leaving at 7:55 AM (Pacific time) and arriving at 4:15 PM
(Eastern time).  The apparent time difference is 8:20.  But the real
time difference is 5:20.
   The return trip is complicated by a stop-over in Salt Lake City of
one hour.  ( I couldn't find a non-stop from JFK to SFO.  Seems like
there should be one, doesn't it?)  This flight leaves JFK at 7:10 A,
arr. SLC at 10:10 (MST), leaves SLC 11:10 A and arrives SFO at 12:08
PM (PST).  Flight time: 7:00.
   So you have the comparison times:  W to E, 5:20.  E to W, 7:00.
   Comparing only equivalent flights, namely SLC-JFK and back, the
times are 4:30 and 5:00.  Or a half hour longer on the E to W flight.
   Hope this helps.  (Sorry about the "overkill" on the question!)
Rondo Jeffery


> A patron brought this question to a reference desk in the next
county,
> which has passed it to us:
> "Why would it take a plane flying non-stop from San Francisco to
New
> York longer than the same type of plane flying from New York to San
> Francisco, when weather, speed, wind, and flying conditions are
exactly
> the same each way?"



Rondo N. Jeffery
Physics Department
Weber State University
Ogden, UT 84408-2508