In a letter sent Thursday to Eclipse Aviation customers, Vice President of Customer and Product Support Ken McNamara had good news to share regarding the performance enhancements for the Eclipse 500 very light jet. He said the company has "demonstrated that we have exceeded our performance guarantees of speed and range" for the Pratt & Whitney PW610F-powered twinjet. According to the letter, N505EA which has been retrofitted to the so-called B model configuration -- flew last week with "production-quality performance modifications" and achieved 372 ktas (two knots more than the 370-knot guarantee) and a maximum NBAA IFR range of 1,156 nm (above the planned 1,125 nm with four occupants). "An important fact to remember is that although we have exceeded our targeted performance guarantees, we are not changing the guarantees," McNamara notes. "You will most likely see better then 'book' performance in your aircraft due to the better then forecasted improvements. But we are not guaranteeing the increased performance." He said Eclipse expects that aircraft delivered in mid-April and beyond will come with these improvements, namely larger tip tanks and aerodynamic refinements. Eclipse 500s delivered before this date eventually will be retrofitted with the upgrades. So far the company has delivered only one of the $1.55 million Eclipse 500s, though it expects to deliver some 500 airplanes this year. In late December Eclipse said that nearly 40 of the VLJs were in various stages of assembly, but Eclipse wont be able to deliver aircraft en masse until receiving its Production Certificate from the FAA.