If one went spotting back in the 1970's, one could observe Boeing, Airbus, McDonellDouglas, Convair, Lockheed, Caravelle, many more Tuoplev's and Ilyushins, Dassault, Vickers, BAC1-11, Vickers, Tridents, etc.
There were many manufacturers over there, but nowadays most A/ are only Boeing and Airbus for the non regional airliners.
Why is it that for non regional airliners, Boeing and Airbus have the duopoly? (OK MD did merge into Boeing but this doesn't explain all). Is there a reason to explain this. Its must be really boring being a spotter nowadays as compared to 30 years ago .