In short: Basically the city of Fort Worth and Brandiff Airways all invested heavily into DFW. So to help protect the investments in DFW Jim Wright member of the US house or representatives serving Fort Worth helped pass an amendment to the IATA.
The protocol restricted passenger air traffic out of Love Field in the following ways:
Passenger service on regular mid-sized and large aircraft could be provided from Love Field only to airports within Texas and the four neighboring U.S. states: Louisiana, Arkansas, Oklahoma, and New Mexico. All Southwest flights were then within those states, so the law had no immediate effect on Southwest.
Flights to other states were allowed only on aircraft with 56 seats or fewer.
The Wright Amendment was effective by February 1980 and will be off by October this year.
For more details click on the link below:http://en.wikipedia.org/wiki/Wright_Amendment
Sami can you add that please into the game as your game is based on real life stuff, demand and what aircraft should operate in airports and clearly in Love field (in the game) there is no limitations on what aircraft you could operate and most aircraft which operate from outside the state allowance for e.g. LAX are operated not by reg jets but by narrow bodies which isn't allowed. Please can you fix that.