That tops rival Airbus' year-to-date jet deliveries of 228. The European jet maker said Thursday it delivered 45 jets in May, including three A380 superjumbos.
Airbus said it took in orders for 37 A320s, pushing the single-aisle jet family's order total to 8,400 over its lifetime.
Airbus has 132 net orders across its product lines for the first five months of 2012.
On Thursday, Boeing added an order for five 777s from Pakistan International Airlines and one 777 from an unnamed customer. However, the Chicago-based company also logged a cancellation for four 777s, bringing Boeing's net order total to 420.
Boeing's substantial order lead over Airbus is largely due to the popularity of the company's re-engined 737 MAX, launched in August. Airbus beat Boeing in orders in 2011, having launched the re-engined A320 in late 2010.
In May, Boeing delivered eight 777s, three of the new 747-8, two 767s and 36 of the Renton-built 737.
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