in the UK as well. BEA, whose frequencies were not restricted, responded to the challenge on its three most important domestic routes by scheduling additional flights that departed and arrived at the same time or within 10 minutes of its rival's scheduled departure and arrival times. This had the effect of "sandwiching" British Eagle's flights. BEA's response also included the introduction of trickle loading and subsequent introduction of full onboard catering as well as a separate first class cabin. On 11 March 1964, a BEA Trident 1C operated the Trident's first commercial service, standing in for a Comet 4B that had been scheduled to fly 79 fare-paying passengers from Heathrow to Copenhagen. BEA's regular commercial Trident operations commenced on 1 April 1964. Initially, BEA operated its Tridents in a 79-seat, two-class configuration, comprising 15 first class and 64 tourist class seats. In June 1964, BEA acquired a minority shareholding in Northeast England-based independent regional airline BKS Air Transport. On 10 June 1965, BEA Trident 1C G-ARPR performed the world's first automatic touchdown at London Heathrow on a commercial flight with fare-paying passengers. Another BEA Trident performed the world's first fully automatic landing in fog by a civil aircraft in zero visibility at Heathrow in November 1966. On 26 August 1965, BEA signed the contract for a follow-on Trident order. This covered 15 firm Trident 2Es plus 10 options for delivery from spring 1968. The 2E series was an aerodynamically improved version of the original 1C series incorporating the re-arranged interior of the "hot-and-high" 1E series that resulted in a greater seating capacity, as well as a higher gross weight, increased fuel capacity by providing an additional fuel tank in the fin and more powerful Rolls-Royce Spey engines to fly non-stop from London to Beirut with 90 passengers. In the mid-1960s, BEA's European rivals began placing orders for new "second-generation" jet aircraft, such as the Boeing 727-200 and its smaller stablemate, the 737-200, as well as the Douglas DC-9-30/40. Compared with the Trident, these were more economical, in terms of range, revenue generation and seat-mile costs. Of particular concern to BEA in this context were Air France's plans to replace Caravelles with new 727-200s on most of its London–Paris flights. BEA also had a requirement for a jet to replace Vanguards on the Heathrow–Manchester route to regain traffic lost to British Rail as a result of the electrification of the London–Manchester