Aside from the extra songs such as "When the Tigers Broke Free" and alternate versions of tunes like "In the Flesh?," "Goodbye Blue Sky" marks the first prominent variation between the album and the film. While the song acts as a continuation of sorts for "Tigers" in the movie, it immediately follows "Mother" on the album. Although many have argued about the best possible position for the song, whether after "Tigers" or "Mother," I think the order for each respective project is perfectly suited for the song's multifaceted implications.
On the original vinyl version of the album, "Goodbye Blue Sky" occupied the last slot on the first side of album one (remember that it was a double album). In an interview around the album's release, Waters described the song as being a recap of the first side of album one summing up Pink's life to that point. As Waters says, in it's most simplistic form "it's remembering one's childhood and then getting ready to set off into the rest of one's life." In this position, the song acts as the transition between "Mother" and the more grown up, more world-weary "Empty Spaces." The music is still very peaceful and beautiful, a reflection of the youth Pink is leaving behind, while the lyrics are more of a lament and arguably slightly paranoid. The very vocal stutter on the "Di'
di' di' did" part of the verse belies any sort of composed identity Pink might have created for himself, revealing, if anything, his apprehension at bidding farewell to his own innocence by stepping into the sinful world where he will become an adult. By this interpretation and remembering the symbolism of the color blue as discussed in "the Thin Ice," Pink is saying "goodbye" to the "blue sky" of his childhood innocence and the protection of his mother. Also keeping in mind that Pink was once called "baby blue," his departure from his simplistic and inexperienced infancy is further underscored, specifically marking the transition between his appellation of "Baby Blue" to the more emotionally experienced and sexually charged color (and name) "Pink." As is true until now and for the rest of Pink's life, "the flames are all long gone but the pain lingers on." In other words, while those things which hurt Pink physically, mentally, and emotionally are no longer present in his life (the death of his father is a memory, his schooling days are over [at least in the song's position in the album], he is finally moving away from his mother's protective arms), the scars caused by these wounds are still present and just as painful; each of these pains are more bricks in his wall.
The problem with placing "Goodbye Blue Sky" after "Mother" is that the lyrically charged war images aren't especially applicable. The "frightened ones," "falling bombs," and running "for shelter" just don't carry across that overwhelming sense of war-time immediacy and forced transition when placed directly after "Mother." While the song works on the level of Pink's transition, the war lyrics seem out of place and drawing the usual parallels between Pink and World War II seems strained. Personally speaking, the song works best following "Tigers" in that it acts as both a continuation of the themes of war and loss dealt with in the previous song as well as Pink's own realization of the burdens placed on him by his father, mother, and society as a whole. Directly following the highly emotional account of the father's death, the fear of war is palpable in the lyrics of "Goodbye Blue Sky." Just as England and the rest of the world bid farewell to whatever innocence remained before World War II, Pink, although still a child, bids farewell to his childhood ignorance. Similar to its meaning after "Mother," the song is another transition in Pink's life, between that of youthful unawareness and the self-consciousness of young adulthood. Although Pink is not bidding farewell to everything in his childhood (he still lives with his mother during this positioning of the song), he is saying "goodbye" to what he was once while apprehensively stepping into what he will become.
As with most Pink Floyd songs, "Goodbye Blue Sky" is musically and lyrically deceptive in its seeming simplicity. The quiet music and vocals and the seemingly forthright lyrics can be viewed as the components of a simple transitional song…but narrow interpretation would rob the song and its artistic movie representation of its complex beauty. For me, the most interesting complexity lies in the duality of the lyric "promise of a brave, new world." The most commonly accepted reading of this line equates the "brave, new world" with the positive effects of World War II. Hitler and his fascist regime will be obliterated, thus allowing for the world to technologically progress and mature, becoming a safe haven for all peoples. Yet no matter how intentional, there is a sinister ring to the very same line recalling Aldous Huxley's 1931 novel "Brave New World" that tells of a futuristic utopia in which babies are born from test tubes, trained for their future jobs at birth, and pushed into a homogenized, capitalistic world that has all but destroyed individuality. Such an allusion offers a plethora of interpretations. The "brave, new world" could be a reference to the standardized, Aryan nation that Hitler sought to introduce with his Third Reich. Simultaneously, the very same words could reference what our world has become after World War II, referring to the over-abundance of technology in a worldwide capitalist community as predicted by Huxley in 1931. Every computerized sale at global corporations such as McDonald's, GAP, and Starbucks brings the world one step closer to Huxley's vision of a false utopia. As a result, the individuality of the world's inhabitants is made uniform through technology and the media. The very same technology that produced the atomic bomb that took the lives of 
millions of Japanese people (and continues to show effects on Hiroshima and Nagasaki) is the same technology that allows us to microwave a burrito and watch the latest episode of our favorite television show. I don't mean to launch into a diatribe but rather demonstrate the fear behind our technological world as illustrated in both Huxley's novel and "Goodbye Blue Sky." So when the narrator innocently asks why "we had to run for shelter when the promise of a brave, new world unfurled beneath the clear, blue sky," the answer is that because that "brave, new world" has the potential for being just as flawed and narrow-sighted as the corrupt power we were fighting against. Arguably, the slaughter of millions of Jews by Hitler is nearly equivalent to the destruction of Hiroshima and Nagasaki as well as the sterile world being produced by the very same technology that helped the Allied forces triumph. Such ideas of "mixed blessings" (Huxley - the world is a utopia only in that it erases personal identity; WWII - the atomic bomb ended the war but created moral discord) tie in perfectly with Pink's personal situation. While focusing on constructing his wall, adding each brick as a protection from the outside world, Pink fails to recognize the long-term effects of his self-imposed isolation and his eventual destruction from within his erected barrier.
The movie's depiction of this song is an example of just how powerful animation can be as a medium, allowing for scenes and events that could not be depicted by regular photography. The beginning shots of baby Pink and his Mother both set the time for the war-imagery of the song (the war is still being waged) as well as offer a contradiction between the innocence of England and the world as it was and the destruction that war has brought to the land as illustrated in the animation. As a dove flies into the air, the scene switches to animation and the bird of peace is symbolically torn apart by the German war eagle which gouges a bloody wound in the land and leaves a sulfurous trail in its wake. The eagle gives way to a domineering war-lord that morphs into a metallic factory churning out legions of bombers flying over London and scaring the gasmask-wearing "frightened ones" (portrayed as naked perhaps to illustrate their innocence) into shelters. The bombers turn into crosses just as the Union Jack (the British Flag) sheds its stripes to reveal a crucifix, both suggesting the needless sacrifices made on both sides in the name of war. The brainwashed, mob mentality of the Germans created by the warlord (Hitler and the "higher-ups") sent German youths to their deaths in the name of moral right just as the leaders of the Allies sacrificed the young men of their countries. This is in no way a justification of the actions taken by both sides. Instead, it 
is a vehement anti-war argument. It's only when the dove of peace reemerges from the shattered ruins of the metal factory / warlord that the dead soldiers are able to find peace in death. Like the blood from the cross running down the hill into the drain, the sacrifices of all the men involved are in vain. Gerald Scarfe's animation adds another dimension to the song portraying his strongly anti-war sentiments. For Scarfe and Waters (as illustrated in "the Wall" and the follow-up album, "the Final Cut"), war is little more than glorified chess between two enemies, a battle between political giants displaying the "might" and "power" of one leader over his people; it is a narcissistic fight for "moral right, superiority," and property. The only hope one can have is that in the end, as the dove's rebirth suggests, peace will prevail.
http://www.thewallanalysis.com/goodbyebluesky.html
