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Eagle-eyed passengers onboard 
American Airlines regional flights have spotted the unusual hard table seat that is installed on the final row of Envoy Air and some Republic AirwaysEmbraer E170 airplanes. The situation, first reported and analyzed by Gary Leff at View From The Wing, has raised questions as to why an airline would restrict passengers from reserving this seat.
First of all, the seat is not a malfunction, broken, or awaiting repair; it is due to strict scope clauses for regional flying and the number of crew onboard. American Airlines, the owner of Envoy Air and through capacity purchase agreements with Republic, blocks out the final row of the E170.
A Blocked Out Seat Onboard The E170: What Is Going On Here?
As spotted by travelers and shared on Reddit, there is the final row of the E170 blocked out, meaning that travelers are unable to sit here. This seat has a permanent table in the place of the seat cushion, restricting the plane to a total of 65 seats, versus the standard 66. The reason is that if the plane flew with its full capacity of 66 seats, it would be in breach of American’s pilot union contracts.
As VTFW detailed, the blocking of seat 21F allows the plane to operate within the scope limits, which American has a restrictive covenant for jets that have between 66 and 76 seats, and that the 
oneworld carrier cannot surpass more than 40% of these planes in its mainline fleet operations.
Instead of removing the seat altogether, it is easier for the aircraft operator to preserve the standard cabin configuration and instead have the seat classified as a ‘non-occupiable position’. For the passenger in the back row, they instead have a spare seat next to them, without a cushion, and as a result, a permanent side table.
Keeping A Standard Layout Makes It Easier To Restore The Seat If Required
It is quicker and easier for both Envoy and Republic to operate with the standard set-up of the seat in-situ, but instead restrict its use by removing the seat cushion and adding the table. If the airlines were to proactively remove the seat, it would require custom alterations as the seats share track attachments, trim, and otherwise have regulatory requirements for clearance and crash-worthiness approval.
Keeping the seat as is, it allows the operators to keep the interior practically as close to the standard layout, minus one seat cushion. This can be common practice across airlines that must restrict the total number of seats occupied on a flight, whether this be for operational or regulatory requirements, instead of needing to make costly interior alterations.
As part of American’s pilot agreements, contracts stipulate that due to pilot rules, an airline that is owned and operated, or contracted to other regional carriers, must stick to restrictive clauses which include not exceeding 65 seats; otherwise, it would consume a slot in the lucrative 66 to 76 seat range category.
Does The Scope Clause Impact Regional US Airlines Negatively?
The existing scope clause limits the aircraft types that regional airlines can operate within the US, by factors such as the Maximum Take-Off Weight (MTOW) or the maximum seating capacity of the aircraft.
This is one of the primary reasons why Embraer paused the development of its Embraer E175-E2 regional jet aircraft. Because, despite the aircraft being an upgrade to the already popular E175 jet, the E2 version would exceed the limitations, making it unviable in the US market.
However, I believe that these restrictions essentially prevent regional operators within the US market from upgrading their fleet to more modern and efficient jets, which would also help the carriers reduce their operating costs, due to the fuel efficiencies and economics offered by these jets.
What are your thoughts on this matter? Do you think the scope clause is good for regional operators, or does it prevent these operators from evolving into more efficient carriers?
How Do Scope Clauses Affect The US Airline Industry?
Scope clauses are strict union-negotiated contract requirements that limit airlines to the total number, size, or total seat capacity that major U.S. carriers are permitted to outsource to regional affiliate partners. These clauses are designed specifically to protect the airline’s mainline pilot jobs and wages.
The theory is that scope clauses are designed to minimize the lure of airlines outsourcing regional, short-haul, domestic routes to other lower-cost operators where there is a high volume of travelers. These clauses include several seat caps, which are typically capped for between 66 and 76 seats, making the idea of restricting a single seat on the E170 a smart idea to minimize these lucrative slots in this category.
Since these restrictions continue to influence how U.S. carriers schedule flights and deploy aircraft, they have supported the ongoing popularity of regional aircraft like the E170, E175, or CRJ series, which can be seen across all major carriers like American, 
Delta Air Lines, 
Alaska Airlines, and 
United Airlines. For now, the empty seat in row 21 will remain a permanent fixture so airlines don’t breach the strict covenants.
