Here's a little I had written some time ago:
United Airlines' early years to Europe
Before UAL started flying into Heathrow in April 1991, they had three trans-Atlantic flights each way – UA106/ 105 ORD-CDG, UA128/129 ORD-FRA, UA130/131 IAD-FRA (east/west). Both FRA routes started May 15, 1990 eastbound, with the first westbound service the next day, then ORD-CDG started on August 1. (ORD-FRA initially was flight 126; the others started with the numbers they had at the start of service to LHR.) All used 767-222ERs.
London Heathrow access
But they were hardly a great market presence. London/LHR is to Europe what Tokyo/NRT is to Asia. If you don't get service to London, you have limited market presence and traffic. UA was granted the FRA/CDG routes earlier, but it wasn't until they got London, Heathrow specifically, including some limited through-rights and fifth-freedom rights that they really got into Europe.
It is also rather ironic that UAL purchased the routes from Pan Am, who originally got them years earlier from AOA (American Overseas), a then-subsidiary of American, who later purchased TWA's routes to get back in.
It was not a dramatic start. But it was not until UAL started LHR service that they became a true Trans-Atlantic contender.
CDG or ORY?
There were reportedly some tensions between the French and US authorities about the airport United Airlines would use. The French authorities wanted UAL to land at Paris – Orly (ORY) in order to protect Air France at its CDG base. But the US authorities insisted on being granted rights for CDG for UAL. The French authorities would have agreed only at the very last minute.
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Photo © Rudy Chiarello
Feel free to make corrections/additions!
ATB - Iberia 767