飛(ひ)行(こう)機(き) hikoukiは waまもなく mamonaku見(み)え()な()く() mienakuなった natta。 The airplane soon disappeared from sight. Literal Airplane [topic-は] soon visible-not became. まもなく means 'soon, before long.' 見えなくなった combines the potential 見える ('to be visible') with ~なくなる ('cease to'), expressing the plane gradually disappearing from sight. airplanestransportation~なくなる (cease to)
飛(ひ)行(こう)機(き) hikoukiは waまもなく mamonaku見(み)え()な()く() mienakuなった natta。 The airplane soon disappeared from sight. Literal Airplane [topic-は] soon visible-not became. まもなく means 'soon, before long.' 見えなくなった combines the potential 見える ('to be visible') with ~なくなる ('cease to'), expressing the plane gradually disappearing from sight. airplanestransportation~なくなる (cease to)