ST00912WI

Installation of Model 31A interior as refurbishment to retrofit Learjet models. Held by Avcon Industries INC, which holds 121 approved modifications in all. Last revised April 23, 2019. System: cabin, seats and restraints.

What it applies to

Kind of product: Aircraft
Design holder: Learjet Inc.; Learjet Inc.; Learjet Inc.; Learjet Inc.; Learjet Inc.
Models: Learjet 36A, Learjet 31, Learjet 35, Learjet 35A (C-21A), Learjet 36
Type certificates: A10CE, A10CE, A10CE, A10CE, A10CE
The FAA's record: On the FAA's site

What an approved modification is

A supplemental type certificate is the FAA's approval of a change to a certified design: a new engine or propeller, avionics, an autopilot, floats, a parachute, a larger fuel tank, an ice-protection kit. The company holding it may sell the kit and the paperwork to owners of the listed models; the modification then becomes part of that aircraft's record. The FAA's list says what was approved and for which models, not how many aircraft carry it.

Source: FAA supplemental type certificates (Dynamic Regulatory System). Register counts from the FAA register of October 20, 2026.