“Even the youths shall faint and be weary, And the young men shall utterly fail, But those who wait on the LORD shall renew their strength, they shall mount up with wings like eagles, they shall run and not be weary, they shall walk and not faint” (Isaiah 40:30-31).   

Eagles are efficient in flight.  Wildlife researcher Adam Duerr writes, “Like many people, I am fascinated by bird flight.  Unlike most people, I get to study flight of Golden Eagles for a living.  These large birds move through the landscape primarily by soaring – a style of flying where they hold their wings outward and rarely flap, saving them considerable energy.  Instead of flapping they reply on rising air currents to gain altitude.  Two types of raising air currents provide most lift for soaring eagles.  The first, thermal updrafts, form when energy from the sun heats air at the Earth’s surface and causes it to rise.  Eagles circle within these columns of rising air to gain altitude and then glide out of the thermals to move across the landscape.  The second, orographic updrafts, form when winds are deflected upward by structures such as ridges or hills.  Eagles can soar at relatively low altitude above and along those structures (Fly Like an Eagle? By Adam Duerr, April 9, 2019, americanorinthology.org).  This saves energy.  The Journey North, associated with the University of Wisconsin – Madison Arboretum, had this to say, “It takes a lot of energy to flap such large wings… two scientists who studied eagles, Jon M. Gerrard and Gary R. Bartolotti, write that “Eagles are capable of sustained flapping flight but they usually spend little time doing it.  During the month when Cindy (one of the female eagles they studied) was observed intensively, she averaged less than 2 minutes per hour in flapping flight.  That is not surprising when one considers the large expenditure of energy required by the pectoral and superacoracoid muscles to power the huge wings.  The energy needed to maintain a bird in flat soaring or gliding flight is much less, perhaps a 20^th or less the power needed for flapping.  Therefore, eagles will always choose to soar or glide when possible’” (How Eagles Fly, journeynorth.org).

The wings of an eagle are amazing.  They contain winglets at the tip of their wings which reduce drag.  “Dr. Edward F. Blick, who served as a professor in the School of Aerospace at the University of Oklahoma, did extensive wind-tunnel studies at the university with eagles.  In doing research in 1971, Dr. Blick and his colleagues discovered that the eagle’s six-slotted feathers (at the end of each wing) curve upward in gliding flight.  Wind tunnel measurements demonstrated that this design reduced the size of the vortex (whirling current) that emanates from each wing tip.  This, in turn, reduces drag on the wings and allows the eagle to soar great distances on air currents – without even having to beat its wings.  Professor Blick, impressed with the accuracy of the Bible in this regard, stated: ‘Thus 2,700 years after the scripture in Isaiah was written, science has stumbled onto the same truth’” (Wayne Jackson, Science and the Eagle’s Wings, christiancourier.com).

Airplane winglets (upturned ends of the wings) are an example of biomimicry (design by human engineers which mimics what is found in nature, life science, biology).  “When an airplane is in flight, spirals of air are created at the tip of the wing.  This causes drag, which increases fuel consumption… winglets are the upturned ends of airplane wings.  The shape minimizes drag by reducing the size of the vortices created at the end of the wing.  In addition, as the vortices hit the winglet some of the force is converted to thrust, which helps move the plane… soaring birds have upturned wing tips that maximize lift… improving performance and saving energy” (Aerodynamic Wing Additions Inspired by Birds, asknature.org).  Winglets began appearing on airplanes and became common in private and commercial flight in the 1970’s and 1980’s (What Was the First Airliner to Have Winglets? By Omar Memon, simpleflying.com). 

The renewal of strength is mentioned.  The eagle (and other birds) molt (shed old feathers) and produce new feathers.  This may be a reference (cf. Psalm 103:5).    In the passages before us, there is a contrast.  Difficult times were coming.  Even young men would faint.  Strength would be found in waiting on the Lord, trusting in and serving Him.           

The passage mentions three modes of movement in descending order: flying (mount up with wings like eagles), running, and walking.  This may cover different circumstances in life.  Sometimes we are soaring high.  Sometimes we are running to meet urgent needs.  Life is fast paced.  Sometimes we are walking.  Things move more slowly.  Yet, those who wait on the LORD continue onward.  They do not grow weary (Galatians 6:9).  In the return from Babylonian captivity, the Israelites would first soar to heights of joy.  Then, they would run to make preparation for the return.  Then, they would begin the long walk home (Homer Hailey, A Commentary on Isaiah, p. 340).  We too experience different circumstances in life.  Homer Hailey provides this, “The joyous enthusiasm and hope we experience with conversion, soaring on high as with wings on an eagle, are followed by eager preparation, learning and building a foundation of faith, and running without growing weary; but before the heavenly home is reached, there is yet the long journey of trials and testing – a walk on which the sojourner of faith shall not faint.  In the wearisome and monotonous everyday walk of life faith may at times become dull and hope dim; in such hours look up and grasp a new vision of God and heaven” (ibid).