Chapter 1 — Between Two Runways

The green dot on the approach radar screen blinked slowly, up to half a breath slower than usual — a familiar delay that Ky Boi Thu had learned to compensate for in his mind during ten years of sitting in this position. Outside the glass window of the command tower, mist from the Vinh Ky range was pouring down into the valley, gradually swallowing the mountain contour, leaving a milky white layer hovering just above runway 09/27. Sixteen twenty. Afternoon shift. Flight VT205, an ATR carrying passengers from the east, was at a distance of ten nautical miles and requested to lower its altitude to three thousand feet to prepare for the approach.

"Victor Tango two zero five, Tra Son approaching, descending three thousand feet, keeping direction two seven zero," Boi Thu said into the microphone, his voice steady, his eyes never leaving the blue dot moving slowly on the screen.

"Three thousand feet down, heading two seven zero, Victor Tango two zero five," the pilot's voice replied, clear, precise, nothing unusual.

Next to him, Kha Viet Bach sat in the observation position, his headphones tilted to one side, as was the habit of a trainee not yet used to covering both ears, his eyes glued to the secondary screen. For three weeks he had sat with Boi Thu, taking notes and comparing his judgment with her decision after each command. Today he was assigned to monitor the small flow—agricultural, training, helicopter—while she handled the main flow.

The main screen displayed four targets: VT205 approaching from the east, a civil flight school training flight practicing closed take-offs on the secondary runway, and two distant blurs that the system had not yet assigned codes to — those two dots, Boi Thu knew, were just terrain noise reflected off the western cliffs, something that any beginner would take months to learn to ignore. Tra Son station's SSR had been in operation for eighteen years, its scanning speed was one-third slower than equipment at major airports, and on high humidity days like today, the image on the screen was sometimes up to three or four seconds late compared to the aircraft's true position. She was used to compensating for that delay by adding the distance in her head, a calculation that no one teaches in the textbook but anyone who had been at the station for many years could learn to do it.

The loudspeaker broadcasts the automatic ATIS message, the monotonous voice repeats the wind parameters: direction two or four zero, speed eight to twelve knots per hour, jerking up to eighteen when there is a flow from the mountainside. Boi Thu glanced at her watch and scratched a note in her duty book, a habit she kept for ten years even though she knew every conversation was automatically recorded.

A small beep sounded from the corner of Bach's screen. A new target appeared, less than four nautical miles from VT205's approach, altitude reported at two thousand two hundred feet and rising.

"Miss Thu," Bach said, her voice a bit hesitant, "there... there's a new target, southwest, I haven't seen the flight plan yet."

Boi Thu glanced over. A familiar white, unmarked dot, moving at a speed faster than a typical agricultural aircraft. She pressed the emergency frequency switch button.

"Which station is calling on Tra Son frequency? Please confirm."

There was no immediate response. Three seconds passed — to outsiders, three seconds is nothing, but to someone sitting in this position, three seconds is enough time for a plane to move nearly half a nautical mile.

"Tra Son, this is a unique Hai Au, requesting an emergency landing, there is a critical patient on board, please give priority."

The emergency helicopter pilot's voice was urgent, interrupted, and overlapped just as VT205 was rereading the command to descend. The two voices overlapped each other in the speaker, turning into a series of muffled sounds, with no words clearly audible. Boi Thu frowned, his ears were used to distinguishing between two overlapping channels, but this time they both used the same access frequency because the emergency helicopter had not yet switched to its own channel.

"All stations, stop transmitting, Tra Son approaches and calls Victor Tango two zero five, say again, repeat the previous command."

"Victor Tango two zero five, sorry, didn't hear clearly, confirm descent three thousand feet."

Just as she feared — the ATR didn't get the last part of the sentence, the most important part: keep heading twenty-seven zero to avoid cutting into the traffic flow from the southwest. If the pilot had guessed and turned early in the normal approach direction, their flight path would have crossed right where the incomparable Hai Au was entering.

The radar screen flashed again, a familiar delay that made the helicopter's white dot appear to stand still for a beat and then leap forward — the result of gusts of wind blowing along Vinh Ky's flank, pushing its ground speed faster than anyone in the room expected.

"Bach, how high is Hai Au now?"

"Two thousand six hundred... is increasing rapidly, sister, it's not standing still, there's something..." Bach paused halfway through his sentence, his fingers hovering over the keyboard, his eyes looking from the screen to Boi Thu as if waiting for her to confirm before believing in the number he just read.

That half second of hesitation — Boi Thu didn't have time to pay attention to it, but later she would remember that exact half second more than anything else that afternoon.

She didn't wait. The left hand maintains the main frequency, the right hand reaches for the emergency microphone.

"Victor Tango two zero five, Tra Son approaching, go-around, I repeat, go-around immediately, fly back in the direction of two zero zero, up four thousand five hundred feet."

A short, terrifying silence — a silence that any controller hates, because in that silence no one knows whether the pilot heard or not.

"Go-around, direction two zero zero, up four thousand five hundred, Victor Tango two zero five."

The sound of the engine accelerating echoed vaguely in the background of the radio, a sign that the plane was following instructions. On the screen, the green dot of VT205 changed direction, the altitude began to increase again.

"Hai Au zero two, Tra Son approaching, turn left immediately, direction one eight zero, down one thousand eight hundred feet, avoid the flight coming from the east."

"Turn left one eight zero, down one thousand eight hundred, Hai Au zero two, accept."

The two dots on the screen began to separate, slowly, too slowly for the heartbeat of anyone standing in the room. Boi Thu kept his eyes on the screen, silently counting the shrinking and expanding horizontal distance: two point eight nautical miles... two point three... just as the helicopter's white dot changed direction, the distance began to widen — two point six, three point zero, three point four. The altitude difference when closest to each other was only about six hundred feet, below the minimum separation of one thousand feet according to regulations, at the exact moment the two flight paths seemed to be about to intersect.

No one in the room said anything for nearly a minute after both targets had completely separated, VT205 was being vectored back onto the second approach path, Hai Au no two asked for permission to land on the secondary landing zone far enough away from the main runway to avoid conflict.

Boi Thu just realized he was holding his breath. She exhaled, slowly, trying to keep her breath inaudible over the open microphone.

"Victor Tango two zero five, you're in good position for the second approach, light breeze, nothing to worry about. Sorry for the interruption."

"Thanks Tra Son, it's okay, we're fine," the pilot's voice replied, so calm that it was almost the opposite of what had just happened in the radar room.

Bach removed the headset from one ear, placed his hand on the table, his fingers shaking slightly. He didn't say anything, just looked at the screen, where the two bright dots were now far apart, each dot going in its own direction as if nothing had ever happened.

"I'm sorry," he finally said, his voice small. "I saw the number increasing but I... I'm not sure, I'm afraid the report will be wrong."

Boi Thu did not respond immediately. She looked through the glass window, looked at the fog covering half of the runway, then looked back at the screen, where the radar scan still rotated steadily, calmly, as if nothing had just happened within a five-nautical mile radius of this tower.

“Tell me next time,” she said, her voice returning to normal, though her hands were still pressed a little tighter than necessary on the keyboard. "If you say something wrong, you can still fix it. If you don't say it, no one can correct it."

That sentence came out of her mouth easily, like a sentence she had said to dozens of students before. But there was something about that sentence that made her chest tighten, a familiar feeling that she didn't want to name right now.

The internal phone bell on the duty desk rang, an old, intermittent ringing sound, from a phone whose battery had been replaced countless times. The screen displays the station manager's phone number.

Boi Thu looked at the number that appeared for a moment before picking up the receiver.

"The station is on duty, Boi Thu listens."

Chuong Ba Vong's voice on the other end of the line was slower and heavier than usual. "Come down to my room as soon as the shift is over. Right now."

Stethoscope put down. On the screen, the radar scan still rotated, steadily, calmly as if not even a half second had been stolen from anyone in this room.