Again, the hard part is not to achieve altitude, but velocity.

In the late 1910s, attempts were being made to achieve higher and higher altitudes.

Early Russian space vehicles successfully achieved very high altitudes without going into orbit.

The really big ones, Reds or Golds, could achieve very high altitudes.

He flew Mnementh high and when they had achieved sufficient altitude, they hovered.

To achieve significantly higher altitudes, one needs very large volumes and/or very strong materials with low density that are affordable in bulk.

Powered by compressed black powder motors, some of these rockets can achieve altitudes of over 2000 feet.

Retracting the flaps fully when the aircraft achieves a certain safe airspeed and altitude.

X-prize was all about achieving altitude (and reuse).

Though the normal Su-9 service ceiling was 55,000 feet (16,760 meters), Mentyukov's aircraft had been modified to achieve higher altitudes, having its weapons removed.