A British judge will on Tuesday rule whether Airbus must keep building A321neo jetliners for estranged Qatar Airways in a decision with implications for future multi-billion-dollar jet deals, as their public bust-up returns to London's High Court. Airbus revoked the A321neo deal in January in retaliation for Qatar's refusal to stop taking A350s in a separate legal and safety dispute over damage to the surface of the larger jets. The knock-on decision to cancel the A321neo deal alarmed some airlines, with the head of the IATA describing it as a "worrying" development in a corner of the market where Airbus enjoys the bulk of new orders. The head of Dubai's Emirates has said he is "not unsympathetic" to its main Gulf rival over the A321neo fallout. Airbus says the two contracts are connected by a "cross-default" clause that allows it to pull the plug on one deal when an airline refuses to honour the other. It has accused Qatar Airways, the A350's biggest customer, of airing invalid safety concerns to avoid taking jets at a time of weak demand, and to activate a $1b compensation claim. Qatar says it was right to stop taking A350 deliveries over what it describes as genuine safety concerns by Doha's regulator over gaps or corrosion in a sub-layer of lightning protection left exposed by cratered paint on over 20 grounded A350s. It says the cross-default clause does not in any case apply. Airline officials worry the A321neo case may set a precedent allowing disputes to ricochet from one contract to another, tightening the grip of plane giants Airbus and Boeing.<br/>