Airline A can have 100% coverage everywhere in the world and be the largest airline. But if Airline B enters a specific route, there is no advantage to a customer whether they ride with A or B for that specific route. This is why there are so many entrants into the industry.
The biggest factor to the lack of durable profits in the airline industry isn’t labor or unions. It’s the ease of entry into the market which puts tremendous pressure on price. There are no substantial barriers to entry, prices go down until profits are close to zero. So in classical value based investment lingo, it is an industry with no competitive advantages.
The airlines industry in aggregate has never had a ROIC greater than its cost of capital over the long term (>1 yr) for the lifetime of the industry.