SAO PAULO (Reuters) - U.S. regional airline Republic Airways signed a letter of intent to buy 100 E175 passenger jets made by Brazil's Embraer SA EMBR3.SA, the two companies said at the Farnborough Airshow on Tuesday.

Republic said the deal would include an option to convert to Embraer’s latest E175-E2 aircraft, with purchase rights for an additional 100 E175 aircraft.

The contract has a value of up to $9.3 billion based at current list prices if all purchase rights are exercised, the airline said.

Swiss airline Helvetic Airways ordered 12 E190-E2 passenger jets, with options to buy another dozen of the same aircraft or convert to the longer E195-E2 aircraft.

The new planes, worth $1.5 billion at list prices if Helvetic takes all 24, will begin substituting the carrier’s Fokker 100 and current-generation E190 aircraft between late 2019 and early 2021.

Brazil's Azul AZUL.N also said it signed an order to buy 21 195-E2 aircraft worth $1.4 billion.