[UPDATE_PASSENGER](state, { id, form: passenger, fieldName }) {
    const hasBirthdayField = has('birthday', passenger.fields);

    let updatedPassenger;
    let newState = evolve({
      fields: {
        passengers: map(
          (p) => {
            if (p.id === id) {
              updatedPassenger = mergeWithKey(
                (k, l, r) => (k === 'fields' ? merge(l, omit(SWAP_FIELDS, r)) : r),
                p,
                passenger
              );

              if (hasBirthdayField) {
                updatedPassenger = resetDocuments(updatedPassenger);
              }

              if (hasBirthdayField) {
                updatedPassenger = {
                  ...updatedPassenger,
                  isAdult: isAdult(passenger),
                };
              }

              return resetChildCheckbox(updatedPassenger);
            }
            return p;
          }
        ),
      },
    }, state);

    if (hasBirthdayField && (!fieldName || fieldName === 'birthday') &&
      isValidBirthday(updatedPassenger) &&
      needSwap(updatedPassenger)
    ) {
      const passengers = compose(
        filter(
          converge(
            or,
            [compose(not, isValidBirthday), needSwap]
          )
        ),
        getPassengers
      )(newState);
      const passengerAge = getPassengerAge(updatedPassenger);
      const groupedByAge = groupBy(
        compose(
          age => (isNil(age) ? -1 : age),
          getFormAge
        )
      )(passengers);
      const withSeats = getWithSeats(passengers);

      let swapOnlyAge = false;
      let anotherPassenger;

      if (DISABLE_AGE_VALIDATION || isAdult(updatedPassenger)) {
        swapOnlyAge = hasSeats(updatedPassenger);
        anotherPassenger = withSeats.shift();
      } else {
        anotherPassenger = groupedByAge[passengerAge].shift();
        swapOnlyAge = hasSeats(updatedPassenger) === hasSeats(anotherPassenger);
      }

      if (anotherPassenger) {
        newState = evolve({
          fields: {
            passengers: map(
              cond([
                [propEq('id', anotherPassenger.id), evolve({
                  fields: merge(__, getSwapFields(updatedPassenger, swapOnlyAge)),
                })],
                [propEq('id', updatedPassenger.id), evolve({
                  fields: merge(__, getSwapFields(anotherPassenger, swapOnlyAge)),
                })],
                [T, identity],
              ])
            ),
          },
        })(newState);
      }
    }

    return newState;
  },