What is the Sabre's '6-3' wing?

Short answer

It is the extended leading-edge modification that, in August 1952, replaced the Sabre's automatic slats with 6-inch extensions at the wing root tapering to 3 inches at the tip. With it, wing area grew from 287.9 to 302.3 square feet.

Published: November 4, 2026 · Updated: November 4, 2026 · Edited by Above Ten Thousand · Editorial policy

F-86Fs 51FIW over Korea 1953

Slats that failed at high altitude

The Sabre's aerodynamically-operated leading-edge slats had proven beneficial during take-off and landing, but in high-altitude engagements with MiG-15s they proved troublesome, because they caused early buffet, ahead of the stall, accompanied by a sudden loss of speed.

Six inches at the root, three at the tip

In August 1952, project engineers removed the leading-edge slats from three Sabres and perfected the extended leading-edge modification, also fitting a wing fence. The aerodynamic slats were replaced by 6-inch extensions at the wing root that tapered down to 3 inches at the tip: hence the name "6-3" extended wing. Total wing area grew from 287.9 to 302.3 square feet.

What changed in flight

At high altitude the new wing design worked perfectly: pilots could cruise comfortably at 49,000 feet and Mach 0.9. The modification brought an increase of roughly 20 knots in the aircraft's take-off and landing speeds. A variant with a more powerful engine and the larger "6-3" wing, without leading-edge slats, totalled 2,239 examples. The Mk 31 variant, of which 21 were built, combined the 6-3 wing with the Avon 20 engine.