Not quite sure that is how it works… its banks that take the risk of currency dealing for the airlines, it more works in terms of this:
First of all airbus makes about 20 billion euros over 5000 orders. The mean would be 40 million euros. This is important, because there are very few billion euro deals. So lets call it a 200 million dollar order made by United Airlines for 10 airplanes, which is 2000 full contracts to buy. I am sure United Airlines do not have a forex dealer on their paybooks. Instead, they just call up a variety of banks to ask what the best rate of euros to dollars is.
Societe Generale say they can do it for 1.33241. Citibank say they can do it for 1.33235. Santander say they can do it for 1.33229. Now the United Airlines takes Santander’s offer because its the best price for euros. It is Santander’s forex traders that are going to try and get a better price than 1.33241 to make their commission, not United Airlines. Hence if they can buy the pair at 1.33129, they have made 10 pips profit, or $200 000 on the trade of 2000 contracts. SG have already taken the dollars off the United Airlines account, and paid Airbus in euros essentially on credit. Now they need to make a profit on the trade of that 10 pips. They hence place their sell order at 1.33129 for those pips. Not further away, because although they want profit, they want to get filled, because if they don’t get filled they are looking at being 200 million in debit. They place the order where their traders expect will be a high probability area to get filled.
Order flow works because 2000 full contracts is a lot of money, and buying 2000 full contracts would cause a huge spike. Santander do not want to pay any more 1.33129, so they are buying anything up to 1.33129. So every time the market hits 1.33129 and below, 300-800 contracts are bought up of the limit order, leaving another 1200 or so orders to fill. This will allow 2-3 bounces off this line. And of course, Santander have probably have some orders from Pfizer, Thomas Cook, General Motors, Dominoes Pizza, amongst others making up more contracts over a month.
During news times, if the news is good for the dollar/bad for the euro, Santander would see that as a great opportunity to buy into the news, making their 10 pips for all their contracts and being flat. If the news is bad for the dollar/good for the euro, and the market is in an uptrend, equally, Santander may have to buy all their orders because they won’t see their price, and they may take less profit or a loss. eg: If SG set their buy orders slightly above Santander, Santander may have to hurry to buy to not make a loss, hence a sudden upmove in price.
In the other direction, Air France is buying Boeing’s off Boeing, and they equally call up their banks for the best deal, and are buying dollars with their euros. Their best offer is 1.38001 from SG, so SG will be trying to sell their contracts a place where they will be filled, yet will net them pips. Hence the orders flow from one order to the next.