No, a conventional jet plane, as commonly understood, cannot break free from Earth's gravity and travel into space on its own. Jet planes rely on the Earth's atmosphere for lift and propulsion, and they are not designed to operate in the vacuum of space.
To escape Earth's gravity and reach space, a vehicle needs to achieve a speed known as the escape velocity, which is approximately 40,270 km/h (25,020 mph) at the surface of the Earth. Jet planes are incapable of reaching such high velocities due to limitations imposed by aerodynamics and the properties of their engines.
For space travel, specialized vehicles such as rockets or spacecraft are required. Rockets are designed to generate high thrust and achieve the necessary speeds to break free from Earth's gravity. These vehicles typically have powerful engines and stages that are jettisoned as their fuel is depleted, allowing them to reach orbit and beyond.
Once in space, spacecraft can maneuver and travel under the influence of other celestial bodies' gravity or by utilizing their own propulsion systems, such as ion engines or thrusters.
In summary, while jet planes are capable of reaching high speeds within the Earth's atmosphere, they are not capable of overcoming Earth's gravity and traveling into space.