The chart here (albeit somewhat dated) portrays the historic experience of several large airplane programs. The time from first flight to first aircraft loss is reflected by the horizontal lines. It is seldom a matter of whether an aircraft will be lost or not, but when that loss occurs and what are the program effects.

If the loss occurs very early in the R&D or flight test phases the consequences could be cancellation of the project entirely. This is especially true when the program is controversial or politically sensitive. The loss of momentum which can result is often enough to jeopardize the whole project, as well as serve as fodder to the critics just looking for an excuse to cancel the project.

A few decades ago, when airplanes were not as expensive as they have become today, the number of test models available were greater. But we can no longer afford to build half a dozen or more test vehicles. Sometimes the dollars available will support barely three or four, so the consequences of losing one, for whatever reason, can be especially significant.