I would recommend updating your leaflet version to 1.7.1 which is the latest, and note that there are differences between leaflet 0.7 and 1+.

About your popup not opening the link, it's because you set the url as text, and not as a link.

You should do this to create a link:

marker = new L.marker([planes[i][1],planes[i][2]])
            .bindPopup(`<a href="${planes[i][0]}" target="_blank" rel="noopener noreferrer">whatever text you want to display for your link</a>`)
            .addTo(map);

You can use window.open():

<a href="javascript:window.open('some.html', 'yourWindowName', 'width=200,height=150');">Test</a>

Or:

<a href="#" onclick="window.open('some.html', 'yourWindowName', 'width=200,height=150');">Test</a>