• Russia's air-dropped bombs are a major threat to Ukraine's soldiers and civilians, said military experts.
• The heavy airplane bombs are "particularly vexing" for air defense systems built to strike lighter targets. 
• Modified "glider" bombs have been fitted with GPS systems.

Russia's Soviet-era airplane bombs present a lethal challenge to Ukraine because they are difficult to intercept even using the most advanced air defense systems,  military experts say.

Oleksiy Melnyk, from the Kyiv-based think tank Razumkov Center, said that combatting air-dropped bombs was "particularly vexing" for Ukraine.

Hi-tech air defense missiles are designed to strike more lightweight targets and are ill-equipped to counter the bombs' old, heavy iron construction. The bombs' dense build and Russia's ample stocks are a significant problem for Ukraine, he said. The powerful bombs can weigh from 1,100 to 2,200 pounds.

Melnyk told Insider that the "dumb" freefalling bombs are dropped from an aircraft during horizontal flights or with the plane's nose up or down. He said the plane's alignment and "altitude will further define the ballistic trajectory." 

The accuracy of such bombing is poor, but Melnyk said the Russians are not overly concerned about collateral damage.

The 30-50-year-old bombs are still robust, Melnyk said. There sheer size means they are "not a big problem to detect, but the problem is to intercept," he said.

The bombs are rarely in the air for a little more than a minute, and unlike cruise missiles or attack drones, they are hard to track, appearing as little dots on radar screens that soon disappear. This makes them a weapon that the latest air defense systems, like the much-vaunted US Patriot missiles, were not designed to combat, military experts say.

Dropping the vintage bombs poses challenges to the Russian military, however. The distance from which you can strike the enemy is low, forcing aircraft to fly into the danger zone of the enemy's air defense systems. As a result, the Russians have had to adapt.

Old bombs with new guidance systems deliver "devastating hits" 

Russia is modifying its simple bombs, equipping them with guidance systems to create cheap and effective substitutes for expensive guided missiles.

The system is similar to the JDAM-ER kits sent to Ukraine by the US, which converts existing unguided bombs into precision-guided munitions.

The vintage bombs are fitted with gliding propellers and GPS systems and fired from a longer distance. They can reach a target of 30 miles away, out of range of most of the air defense systems on the frontline. These systems are more precise, and the payloads are so huge they can wreak substantial damage.

The system has been used to equip old Soviet FAB-500М-62 gravity bombs, which Russia has an abundant supply of, with a simple satellite guidance system and "wings," Insider previously reported, and fired from Su-34 and Su-35 jets.

"Trying to intercept these bombs isn't effective. It's not even rational. The only way out of this situation and the only way to stop it is to attack the planes that launch these bombs," said Yuriy Ignat, spokesman for the Ukrainian Air Force, per The New York Times.

Hence, Ukraine's repeated insistence that it needs the US-built F-16 fighter jets in its arsenal.

Melnyk told Insider the bombs show how Ukrainians "have to deal with a ruthless enemy, especially when we talk about collateral damage."

Most of the damage inflicted by these bombs has been on civilian infrastructure, and most casualties have been civilians, which "produce huge psychological effects on the civilian population," he said.

However, in April, the Kyiv Independent reported that the upgraded guided or gliding bombs were also being used against Ukraine's military formations to "deliver devastating hits upon Ukrainian lines and the rear front."

The bombs also make economic sense to President Vladimir Putin's military planners. The guidance kit costs less than two million roubles, about $24,000, according to Russian media. By comparison, a single Russian Kalibr cruise missile is worth nearly $6.5 million.

"This is the evolution of the air war. They first tried cruise missiles, and we shot them down. Then they tried drones, and we shot those down. They are constantly looking for a solution to strike us, and we are looking for one to intercept them," said Lt. Colonel Denys Smazhnyi of the Ukrainian Air Force, per The New York Times.