"KAC has agreed to an offer by Boeing to buy 10 Boeing 777-300ER jets," chairwoman Rasha al-Rumi said in a statement carried by the official KUNA news agency, which gave no details on the value of the deal.
The offer was accepted after securing all necessary official approvals and the contract will be signed soon, Rumi said.
Delivery of the long-range, wide-body planes will begin in November 2016.
In February, loss-making KAC signed contracts with Airbus to buy 25 planes in the first order for new aircraft in more than 20 years.
The airline, which is slated for eventual privatisation, has an ageing fleet of 15 Airbuses and two Boeings.
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Under the deal, KAC will buy 15 A320neo aircraft and 10 A350-900s, with an option to buy five more of each. Delivery is to commence in 2019.
Under a second contract, KAC will lease seven A320s and five A330s, with delivery due to start next month.
The value of the deals was not disclosed but local media put the figure at around $4 billion (2.9 billion euros).
In addition to modernising its fleet, the KAC wants to become profitable before offering a 40 percent stake to a local or foreign investor.
It has posted losses in all but one of the past 21 years, amounting to a total of more than $2.7 billion (two billion euros), which has been covered by the government.