New York to Boston without motor trouble. But the trouble is
inevitable sooner or later. When it comes to an automobile it is
trifling. The driver gets out and makes his repairs by the
roadside. But if it comes to the aviator it brings the
possibility of death with it every time. If his motor stops he
must descend. But to alight he must find a long level field, with
at least two hundred yards in which to run off his momentum. If,
when he discovers the failure of his motor, he is flying at the
height of a mile he must find his landing place within a space of
eight miles, for in gliding to earth the ratio of forward
movement to height is as eight to one. But how often in rugged
and densely populated New England, or Pennsylvania is there a
vacant level field half a mile in length? The aviator who made a
practice of daily flight between New York and Boston would
inevitably meet death in the end.

The criticism is a shrewd and searching one. But it is based on the
airplane and the motor of to-day without allowance for the
development and improvement which are proceeding apace. It
contemplates a craft which has but one motor, but the more modern
machines have sufficient lifting power to carry two motors, and can
be navigated successfully with one of these out of service.
Experiments furthermore are being made with a device after the type
of the helicopter which with the steady lightening of the aircraft
motor, may be installed on airplanes with a special motor for its
operation. This device, it is believed, will enable the airplane
so equipped to stop dead in its course with both propellers out of
action, to hover over a given spot or to rise or to descend gently
in a perpendicular line without the necessity of soaring. It is
obvious that if this device prove successful the chief force of the
objections to aerial navigation outlined above will be nullified.

The menace of infrequent landing places will quickly remedy itself
on busy lines of aerial traffic. The average railroad doing business
in a densely populated section has stations once every eight or ten
miles which with their sidings, buildings, water tanks, etc., cost
far more than the field half a mile long with a few hangars that the
fliers will need as a place of refuge. Indeed, although for its size
and apparent simplicity of construction an airplane is phenomenally
costly, in the grand total