An investigative reporter would have no trouble documenting this: try to buy a ticket from O'Hare to San Francisco (for example) cheaper than from, say Columbus connecting at O'Hare and the same flight to SFO. Maybe 6 months ahead the O'Hare-SFO flight isn't "blocked" completely and 4 or 5 seats might be available. A lazy reporter asks United for the fare, gets a cheap quote, but a reservation is not available closer to the departure date.
If Airline X offered cheap flights from O'Hare to MSP (Twin Cities), United, American, and Delta would again unblock reservations and lower fares -- to exactly the same price within hours! Without contacting each other?
It is hard to see why Chicago area businesses and the City fathers and mothers think 'This is good for business.' A cynical reporter might check how much United Airlines PACs and executives contribute to election campaigns. Equally, I bet, to Mayor candidates favoring less air pollution and those opposing more regulation.
Is there a safety component? Flights close together (both space, runway separations and headings; and time, operations oer hour per runway) are never both safer and less costly. Taxpayers pay for Federal services --FAA, TSA, Customs, Immigration, ATF, etc. Airport capital and operating costs are higher per flight and funded by bonds, airline leases and fees, and user fees. Does that explain high fees and fares paid by O&D passengers? How do airlines recoup gates lease payments and landing fees? Could it be 'overhead,' a % of ticket revenue?
The "industry" includes, of course, the airport management employees and policy-makers the contract-operators, the aircraft and airport maintenance contractors, the aircraft, jetway, tractor etc. manufacturers. An investigative reporter could track career paths: I think the staffer who aviods noise mitigation or air pollution fines moves up or on to another airport more quickly than a staffer that asks for a costly noise or pollution study. What do you thnk, Jon?
Why are O'Hare management quotes so dismisive of noise complaints? The airport-neighbor is out-gunned on the PR-media front on noise. The airlines have many 'friends' in high places. But, more noise, louder and more frequent overflights, are a sure sign of more air pollution and more safety risk.
The FAA/EPA can't hide from the GHG and carbon footprint treaties, and the FAA and the NTSB can't hide from crashes or the many safety risk management failures and overuse of runways. Not while FAA and the airlines are sucking up $trillions from the national treasury (Next Gen, PBN) to avoid accidents -- and every contract is over-run, years behind schedule, and adjusted annually to move costs from the airlines to the FAA.