Activities that are done in formation are done in a pattern by a number of people, vehicles, etc. moving together.

marching in close formation 以紧凑的队形前进

When birds fly in formation, they often change which bird is leading.

In training, soldiers jog in formation.

The marching band got in formation and tuned up before the parade began.

The whole troupe danced in formation.

Six aircraft flew in tight formation over the palace, leaving plumes of red, white, and blue smoke behind them.