The U.S. aircraft register, updated daily
Parts

First

No failure report names the first. 4 FAA approvals let 1 company make a replacement first, Interactive Flight Technologies INC holding the most (4).

Approved replacement parts 4 parts manufacturer approvals

A parts manufacturer approval (PMA) lets a company other than the aircraft's maker make a first and sell it as an approved part for the models named. These are the companies holding such approvals for a first:

For these models most: Boeing 747 (4).

MakerPartReplacesFitsGrantedStatus
Interactive Flight Technologies INCFirst/Business Class Lower Arm Assembly, RH 10000415-2Modification PartBoeing 747-3001997-11-17current
Interactive Flight Technologies INCFirst/Business Upper Arm Head Assembly, RH 10000414-2Modification PartBoeing 747-3001997-11-17current
Interactive Flight Technologies INCFirst/Business Class Lower Arm Assembly, LH 10000415-1Modification PartBoeing 747-3001997-11-17current
Interactive Flight Technologies INCFirst/Business Upper Arm Head Assembly, LH 10000414-1Modification PartBoeing 747-3001997-11-17current

Sources: the FAA's service difficulty reports since 1995 (a report is a part that failed and was fixed, as filed by an airline, repair station or owner; the count shows reporting as much as reliability) and the parts manufacturer approvals in the FAA's Dynamic Regulatory System. The part name is the reporters' and the approval holders' own words, reduced to the first plain words so that spellings meet.