Pretty impressive.
The following video was filmed from aboard the NF-5A #3 of the Turkish Stars (Turkish: Türk Yıldızları), the aerobatic demonstration team of the Turkish Air Force during an airshow.
The footage includes captions that let you understand what happens during the “2×2 cross” maneuver, when the #1 and #3 aircraft cross with the #2 and #4 coming from the opposite direction at an altitude of around 270 feet above the ground and a relative speed of about 1,600 km/h.
Towards the end the clip you’ll see how close the aircraft of the two section pass one another.
Enjoy.