The Dubai Airshow began on Sunday with plane orders worth over $US100 billion for Boeing and Airbus from Gulf carriers.
Etihad Airways began the show with a $US25.2-billion order for Boeing planes, including 25 777Xs and one 777-200 freighter.
The deal also included an order for 30 units of 787 Dreamliners, making the fast-growing carrier the largest single customer of the medium-body plane.
The airline also announced it was taking an option to purchase a further 26 planes from Boeing.
"Today is an important day in the history of Etihad," said chief executive James Hogan.
Emirates Airline followed shortly afterwards by placing orders with both the manufacturers, in twin deals valued at $US99 billion, 80% of which were with Boeing. No details were given on the figure that includes the engines.
The airline ordered 150 Boeing 777X planes, including 35 777-8Xs and 115 units of the 777-9X.
Emirates also announced a commitment by flydubai, its budget sister company, to buy up to 100 Boeing single-aisled 737 MAX.
Qatar Airways also signed a letter of intent to buy 50 Boeing 777Xs valued at $US19 billion.
The airline said it had also ordered five A330 freighters from Airbus, which are valued at about $US1 billion according to list prices.
Chief executive Akbar Al-Baker said the order was accompanied by an option to add eight airliners, which would put the overall price of the deal at $US2.8 billion.