B737 - numbers 4 and 5 windows
 

Hi..

What was the originaly function of the number 4 and 5 windows of the B 737 family??
I´ve heard several kinds of explanation like, group flights, or navigation by stars, and a way to see the horizon line during a turn.

What is the correct version??

Your third description sounds the best to me.

The forward fuselage of the 737 was the same as the 707 and the KC-135. The no's 4 and 5 windows were there so that the KC-135 crews could see the underside of another 135 during in flight refueling.

Rgds Dr I

From Wikipedia.....

Most 737 cockpits are equipped with "eyebrow windows" positioned above the main glareshield. Eyebrow windows were a feature of the original 707. They allowed for greater visibility in turns, and offered better sky views if navigating by stars. With modern avionics, they became redundant, and many pilots actually placed newspapers or other objects in them to block out sun glare. They were eliminated from the 737 cockpit design in 2004, although they are still installed in military variants and at customer request. These windows are sometimes removed and plugged, usually during maintenance overhauls and can be distinguished by a metal plug which differs from smooth metal which appears in later aircraft that were not originally fitted with the windows.