  Measuring gravity from an aircraft is essential in geodesy, geophysics and
exploration. Today, only relative sensors are available for airborne
gravimetry. This is a major drawback because of the calibration and drift
estimation procedures which lead to important operational constraints and
measurement errors. Here, we report an absolute airborne gravimeter based on
atom interferometry. This instrument has been first tested on a motion
simulator leading to gravity measurements noise of 0.3 mGal for 75 s filtering
time constant. Then, we realized an airborne campaign across Iceland in April
2017. From a repeated line and crossing points, we obtain gravity measurements
with an estimated error between 1.7 and 3.9 mGal. The airborne measurements
have also been compared to upward continued ground gravity data and show
differences with a standard deviation ranging from 3.3 to 6.2 mGal and a mean
value ranging from -0.7 mGal to -1.9 mGal.
