Place the A4 paper vertically on a flat surface
Fold the paper in half lengthwise
Unfold the paper
Fold the top two corners inward to meet the center crease
Fold the new top edges inward again to meet the center line
Fold the paper in half along the center crease
Fold one side down to form a wing
Flip the plane over
Fold the other side down to match the first wing
Adjust both wings so they are even
Flatten all folds firmly