Does anyone know the differences betweeen US Air's First and Envoy class on their flights to Israel?
I have tried contacting USAir to no avail.

US Airways does not offer First Class on any of its international routes. "Envoy class" is their name for business class.

I haven't flown on their int'l business in years. I am told that they are gradually renovating their a/c, moving from 80's-style Barcalounger seats to horizontal (fully-flat) sleeper seats.

They are the same.

Your flight would be an A330-200.

go to usair.com and select Travel Tools and then select In the Air. Click on the Envoy link and see pix of the seats.

The link for first class explains that it is available on flights within N.America.

When I went to choose a flight to Israel, they offered a choice of both Envoy and First Class. I think they partner with Lufthansa on these flights (although it is a direct flight)

schmerl, some of the flights that US Airways sells are operated by Lufthansa, even though they have a US Airways flight number. That's called a codeshare.

All of the Lufthansa-operated flights to Israel from the US require a plane change in either Frankfurt or Munich. Most Lufthansa flights from the US to Germany offer First Class and business, though some offer only business class. All the Lufthansa flights from Germany to Israel offer First Class.

It would help if you told us what city you're starting in.

I'm traveling from Philadelphia to Tel Aviv.
Thanks for all your help.

I've got it now. When I went into USAir site yesterday, I got totally different options than I'm getting today. The non-stop flight from US Air are the Air buses which have the envoy class which looks fantastic!